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Do the school nutrition programs supplement household food expenditures?

I. Introduction

The objectives of the National School Lunch Program (NSLP) and the School Breakfast Program (SBP) are to provide nutritious meals to school children and to create expanded outlets for domestic agricultural products. A critical factor in determining whether the objectives of the programs are satisfied is the extent to which the school nutrition programs supplement the normal food consumption of households, as measured by the household' expenditures on food. Supplementation of households food expenditures occurs when the value of the benefits received through the NSLP and SBP does not lead to a completely offsetting reduction in the household's expenditures on food from other sources.

Two earlier studies have examined the supplementation of household food expenditures by the NSLP and SBP. However, the findings from those studies cannot be considered conclusive because of the use of a specialized sample - households of 8-12 year-old school children in Washington State (West and Price 1976) - and an unusual model specification - the exclusion of expenditures for food at school from the total food expenditures dependent variable in the model (Wellisch et al. 1983a,b).(1)

This paper uses data from the 1980-81 National Evaluation of School Nutrition Programs (NESNP) to examine the impact of the NSLP and SBP on household food expenditures, controlling for possible selection bias that may arise because of unmeasured differences between program participants and nonparticipants in their preferences for food. The paper is organized as follows. Section II provides a brief description of the school nutrition programs and describes the NESNP data. Section III presents the statistical model for the analysis of the impact of the NSLP and SBP on food expenditures. The estimation results are reported in Section IV, and Section V presents the summary and conclusions.

II. The School Nutrition Programs

Under the NSLP and SBP, there are two levels of program participation.(2) First, educational institutions - public and private nonprofit schools(3) and public or licensed nonprofit residential childcare institutions - are eligible to receive cash and commodity assistance under the NSLP and the SBP for providing meals to school children. Each eligible institution may choose to provide the NSlP, the SBP, both programs, or neither. In FY 1981, the NSLP was provided in 81 percent of all schools, serving approximately 92 percent of all school children. In contract, the SBP is provided in many fewer schools than the NSLP. Only about 33 percent of all schools, serving 39 percent of all school children, provided the SBP in FY 1981. With few exceptions, the schools that provide SBP meals also provide the NSLP.

At the second level of program participation, students enrolled in schools that provide the NSLP and/or SBP are eligible to receive or purchase a program meal. for students with family incomes at or below 130 percent of the poverty threshold, the school meals are available without charge. Reduced-price meals are available to students with family income that falls between 130 and 185 percent of the poverty threshold, while students from families with incomes above 185 percent of poverty pay full price for the school meals.(4) Of the meals served under the NSLP in FY 1981, 41 percent were provided free and 7 percent were provided at reduced price. The remaining 52 percent of the meals were served at full price.

Free meals comprised a much larger component of the SBP meals (81 percent), while the proportion of reduced-price meals was about the same as under the NSLP. Only 13 percent of the SBP participants paid full price for their meals in FY 1981.(5) The greater proportion of free meals served under the SBP reflects the high concentration of schools participating in the SBP in poorer school districts. Under the federal reimbursement structure of the SBP, an additional per meal payment is made to participating schools that are designated as in "severe need" - schools in which 40 percent or more of the lunches served are free or at a reduced price. Approximately 44 percent of the schools providing meals under the SBP in FY 1981 qualified for the severe need reimbursement rates.

Overall, student participation in the NSLP during a typical week was about 80 percent in Fall 1980. During the same period, participation in the smaller SBP was about 28 percent of all eligible students (Wellisch et al. 1983a).

III. Statistical Model

The model that is estimated consists of a food expenditure equation based on a linear Engel relationship: (1) F = [X.sub.i alpha] + [beta.sub.1 LS.sub.i + beta.sub.2 BS.sub.i + epsilon.sub.i] i = 1, 2, . . . , N

where [F.sub.i] food expenditures of the ith household: [X.sub.i] is a vector of the ith household's characteristics (including income); [alpha] is a vector of parameters to be estimated; [LS.sub.i] and [BS.sub.i] are the value of the subsidies received by the ith households from the NSLP and SBP, respectively; [BETA.sub.1] and [BETA.sub.2] represent the marginal effects of the benefits from the NSLP and the SBP, respectively, on household food expenditures; and [xi.sub.i] is a random disturbance term. Since the households that choose to participate in the NSLP or the SBP are a self-selected group of households that may have greater food expenditures than otherwise similar eligible households even in the absence of the programs, the model also includes two program participation equations: (2) [L.sub.j] = 1 if [Z.sub.1j delta.sub.1] + [mu.sub.1j] [is greater than or equal to] 0] j = 1, 2, . . . , N
              = 0 if [Z.sub.1j delta.sub.1] + [mu.sub.1j < 0]
(3) [B.sub.k] = 1 if [Z.sub.2k delta.sub.2] + [mu.sub.2k] [is greater than or eq
ual to] 0]    k = 1,


2, . . . , NB

= 0 if [Z.sub.2k delta.sub.2] + [mu.sub.2k < 0] where [L.sub.j] and [B.sub.k] are binary variables indicating the household's NSLP and SBP participation status, respectively (1 = participant, 0 = nonparticipant); [Z.sub.1j] and [Z.sub.2k] are vectors of households characteristics that affect the NSLP and SBP participation decisions, respectively: [delta.sub.1] and [delta.sub.2] are vectors of parameters to be estimated; and [mu.sub.1j] and [mu.sub.2k] are random disturbance terms. The disturbance terms [xi.sub.1], and [mu.sub.2k] have a multivariate normal distribution with mean zero and covariance matrix:

[Mathematical Expression Omitted]

In order to obtain consistent estimates of [BETA.sub.1] and [BETA.sub.2] and their standard errors, the correlation between the error terms of Equation (1) and Equations (2) and (3) need to be accounted for in the estimation procedure. The major complication of the model arises because some of the households have access to the NSLP but not the SBP (i.e., NB < N, where NB households have access to the SBP and N households have access to the NSLP).

The estimation procedure that is used is a modification of the two-stage sample selection procedure proposed by Heckman (1978) to include two selection equations (Maddala 1983). Terms corresponding to Heckman's "lambda" in the single equation context are derived from the estimation of the two participation equations. These terms are included in the second-stage food expenditure equation to reflect the components of the food expenditure disturbance term that are correlated with participation in each of the programs (and, consequently, are the source of the selection bias).

The first stage involves estimating the NSLP and SBP participation equations [Equations (2) and (3)]. Since the dependent variables in these equations - whether or not any child in the household participates at least once in the particular school nutrition program during a typical week - can take on only two values, the participation equations are estimated using probit. Because of the correlation between the disturbance terms of the two participation equations, those equations are estimated jointly using bivariate probit for those households with access to both programs.

Since the households who have the option of participating in the SBP (that is, the households with access to the SBP) are a subset of those who have access to the NSLP, I estimated two versions of the participation equation. A bivariate probit model of the NSLP and SBP participation decisions is estimated for those households that have access to both programs and thus choose whether to participate in each of the programs. The NSLP- and SBP-lambdas are derived from those equations.

A Univariate probit is estimated for all households that have access to the NSLP but do not have access to the SBP (and, consequently, do not choose whether to participate in the SBP). The univariate probit provides the estimates of the NSLP-lambda for those households that have access to the NSLP but not the SBP. For such households, the SBP-lambda is set equal to zero since the SBP participation decision is not relevant.

The two versions of the participation equations are needed since estimating a single bivariate probit model of the SBP and NSLP participation decisions for all households would imply that all households were choosing whether to participate in the SBP, when, in fact, only about half the households face that choice. Including households that are not eligible for the SBP in the population for which the SBP participation equation is estimated would introduce noise in the estimates that are obtained.

In the second stage of the procedure, the food expenditure equation is estimated using generalized least squares, with the NSLP and SBP lambdas control for the selection bias.

IV. Results

In this section, the data that are used and the specification of the multivariate model are described, followed by the presentation of the estimation results.

A. The Data

The data used for this analysis are from the household survey conducted during the 1980-81 school year under the National Evaluation of School Nutrition Programs. That survey collected data on the households of a nationally representative sample of 5,977 students who attended schools that provided the NSLP.(6) The interview included information on participation in the NSLP and SBP, family food expenditures, and background information, such as family income, family size and composition.(7)

B. The Specification of the Model

The specification of the food expenditure equation and the program participant equations are discussed in turn.

1. The Food Expenditures Equation

The dependent and explanatory variables of the food expenditure equation are presented in Table 1. Appendix Table A.1 provides mean values for these variables.

In interpreting the coefficient estimates on the NSLP and SBP subsidy measures, it is important to note that the dependent variable - the households' total expenditures on food during the past week - does not include the money value of the NSLP and/or SBP subsidies or the money value of home grown food. Consequently, the complete substitution of the households' normal food expenditures by the program benefits would be indicated by a coefficient estimate of - 1, while complete supplementation of normal food expenditures would be indicated by a coefficient estimate of zero. Coefficient estimates between - 1 and zero would imply partial supplementation of the households' normal food expenditures by the school nutrition program subsidies.

The explanatory variables included in the final specification of the food expenditure equation are relatively straightforward and can be divided into following categories:

* Measures of household resources (including the value of the benefits

received under the NSLP and SBP) adjusted for household size

and composition.(8 9)

(1.) By excluding food purchases at school, the household food expenditure measure used by Wellisch et al. includes all of the food expenditures of some households (those with children who receive free school meals or bring a meal from home) and only aprt of the food expenditures of other households (those with children who purchase meals at school). (2.) This section draws on U.S. Senate, Committee on Agriculture, Nutrition, and Forestry (1983). (3.) Private schools which charge average tuition of $1,500 or more per year are not eligible for the programs. (4.) Although the students with family incomes above 185 percent of poverty pay "full-price" for their school meals, those school meals, like the school meals provided for free or at reduced price, are subsidized through the federal commodity assistance program. (5.) The distribution of free, reduced price, and full price meals under the NSLP and SBP has changed little since FY 1981, when the NESNP-1 data were collected. In FY 1987, the distribution of meals by price status under the school nutrition programs was as follows (FNS, USDA, unpublished statistics): (6.) To collect the information on students and their families a three-stage stratified sample designed was used. First, school districts were stratified by poverty level and then sampled within strata; second, public schools were stratified by grade level and then sampled within the selected district; and finally, students were sampled within the chosen public schools. (7.) A second National Evaluation of School Nutrition Programs was conducted during the 1983-84 school year: information on household food expenditures was not collected under that evaluation. (8.) A consistent finding of previous research on household food expenditures is that household size and composition have important effects on food expenditures and must be controlled in such analyses (e.g., Pollack and Wales 1980, 1981; Barnes and Gillingham 1984). A common approach to controlling for household size and composition in food expenditure analyses entails the scaling of household food expenditures (and the income and program benefit explanatory variable) by "equivalent person" units, where the units are constructed by weighting each household member by the expenditure or nutritional requirements of an arbitary household member, generally an adult male. Household size is then defined in adult-male-equivalent units as the sum of the weights applied to each household member. (For examples of studies using this approach, see Devaney and Fraker 1989, Smallwood and Blaylock 1984, Basiotis et al. 1983, Brown and Johnson 1983, Buse and Salathe 1978, and Hymans and Shapiro 1976). In this study, I use relative cost of a nutritionally adequate diet for each household member to obtain an adult-male-equivalent-adjusted measure of household food expenditures. The food plan used as the basis for the AME-adjustment in this study is based on the moderate-cost food plan (MFP) developed by the Human Nutritional Information Service of the U.S. Department of Agriculture. This food plan, which is one of four plans (thrifty, low-cost, moderate-cost, and liberal-cost), suggests the amounts of foods that could be consumed by individuals of different genders and ages to meet dietary standards for a moderate expenditure. (9.) The benefits from the NSLP and the SBP are valued at the amoutn of the federal subsidy for the programs - the per meal dollar value of the cash and commodities contributed to the relevant program minus the amount paid by the child for the meal. Benefits from the Food Stamp Program and WIC are assigned their market value-the dollar value of the coupons or vouchers received by the household.
Definition of Dependent and Explanatory Variables for the Total Household Food E
xpenditure
Equation
Variable                                 Definition
Dependent Variable
  Total food expenditures                Total expenditures on
                                          food at home and away
                                          from home during the
                                          past week per AME
                                          ($/AME)
Explanatory Variables
  Earned income                          Average weekly earned
                                          income for the past
                                          month per AME ($/AME)
  Earned income x SBP availability       The interaction of
                                          earned income and a
                                          dummy variable for
                                          whether the SBP is
                                          available to the
                                          children in the
                                          household (1 = yes,
                                          0 = no)
  Other cash income                      Average weekly cash
                                          income from other
                                          sources (including
                                          assistance programs)
                                          for the past month per
                                          AME ($/AME)
  Other case income x SBP availability   The interaction of
                                          other cash income and
                                          SBP availability
  NSLP benefits                          Average weekly subsidy
                                          value of NSLP benefits
                                          received in a typical
                                          week per AME ($/AME)
  SBP benefits                           Average weekly subsidy
                                          value of SBP benefits
                                          received in a typical
                                          week per AME ($/AME)
  FSP benefits                           Average weekly subsidy
                                          value of FSP benefits
                                          received in the past
                                          month per AME ($/AME)
  WIC benefits                           Average weekly subsidy
                                          value of WIC benefits
                                          currently received per
                                          AME ($/AME)
  Ate home grown food                    Dummy variable
                                          indicating whether
                                          home grown foods were
                                          consumed during the
                                          past week (1 = yes,
                                          0 = no)
  Expenditures unusually high             Dummy variable
                                          indicating whether
                                          amount spent on food
                                          during the past week
                                          was more than normally
                                          spent (1 = yes,
                                          0 = no)
  Expenditures unusually low             Dummy variable
                                          indicating whether
                                          amount spent on food
                                          during the past week
                                          was less than normally
                                          spent (1 = yes,
                                          0 = no)
  Household size in AME                  Number of household
                                          members (AMEs)
  Respondent is Black                    Dummy variable
                                          indicating whether
                                          the respondent is
                                          black (non-Hispanic)
                                          (1 = yes, 0 = no)
  Respondent is Hispanic                 Dummy variable
                                          indicating whether
                                          the respondent is
                                          Hispanic (1 = yes,
                                          0 = no)
  Single household head                  Dummy variable
                                          indicating whether
                                          the household is
                                          headed by a single
                                          individual (1 = yes,
                                          0 = no)
  Meal planner aged 35 years or more     Dummy variable
                                          indicating whether
                                          the meal planner,
                                          assumed to be the
                                          female head (or male
                                          head, if no female
                                          head is present), is
                                          aged 35 years or more
                                          (1 = yes, 0 = no)
  Meal planner completed high school     Dummy variable
                                          indicating whether
                                          the meal planner,
                                          assumed to be the
                                          female head (or male
                                          head, if no female
                                          head present),
                                          completed high school,
                                          but not college (1 =
                                          yes, 0 = no)
  Meal planner completed college         Dummy variable
                                          indicating whether
                                          the meal planner,
                                          assumed to be the
                                          female head (or male
                                          head, if no female
                                          head present),
                                          completed college
                                          (1 = yes, 0 = no)
  Meal planner employed                  Dummy variable
                                          indicating whether
                                          the meal planner,
                                          assumed to be the
                                          female head (or male
                                          head, if no female
                                          head present) was
                                          employed during the
                                          previous week (1 =
                                          yes, 0 = no)
  Region: North Central, South or West   Dummy variables
                                          indicating whether
                                          the household is
                                          located in the North
                                          Central, South, or
                                          West region,
                                          respectively (1 = yes,
                                          0 = no)
  North Central x SBP availability       The interaction of the
                                          region variables and
                                          SBP availability
  South x SBP availability
  West x SBP availability
  Urban area                             Dummy variables
                                          indicating whether the
                                          household is located
                                          in an urban area or
  Suburban area                           a suburban area,
                                          respectively (1 = yes,
                                          0 = no)
  Urban area x SBP availability          The interaction of the
                                          urbanicity variables
  Suburban area x SBP availability        and the SBP
                                          availability variable
  School District: Low poverty or        Dummy variables
  Moderate poverty                        indicating whether
                                          the level of poverty
                                          in the school
                                          district was low
                                          (0-11.9 percent of
                                          children below the
                                          poverty line) or
                                          moderate (12-24.9)
                                          percent of the
                                          children below the
                                          poverty line),
                                          respectively (1 =
                                          yes, 0 = no)
  Low poverty x SBP availability         The interaction of the
                                          poverty status
                                          variables and SBP
                                          availability
  Moderate poverty x SBP availability
  Selection-bias correction terms        The inverse of the
                                          Mill's ratio (lambda)
                                          derived from the NSLP
  NSLP participation                      and SBP participation
                                          equations,
                                          respectively
  SBP participation
  Constant                               Constant term


* A measure of household size of adjust for the economies of scale in

food purchase and preparation associated with larger households.

* Measures of whether the household's food expenditures for the

past week were unusually high or low. These variables are included

as proxies for any unusual events which may have occurred during

the week, such as bulk food purchases, major shopping trips (i.e.,

food purchases that are intended to provide supplies for more than

one week), purchases for a party, or guests eating from the household

food supplies.(10)

* Measures of the characteristics of the household member who

makes the majority of the meal planning and food purchase decisions

within the household. This person is assumed to be the female

household head so long as one is present in the household. For

households headed by a single male, the male head is assumed to

be making the meal planning and food purchase decisions.

* Measures of the social and demographic characteristics of the

household.

* Measures of the geographic location of the household.

* Selection-bias correction terms that are derived from the program

participation equations, described below.

To allow for differences in the food expenditure behavior of households with access to only the NSLP and those with access to both the NSLP and the SBP, several of the explanatory variables were created by interacting a household characteristic variable (e.g., earned income) with a dummy variable indicating whether the SBP was available to that household. A significant coefficient estimate for an interaction variable indicates that there is a structural difference in the food expenditure behavior of the two household groups.

2. The NSLP and SBP Participation Equations

The dependent variables and explanatory variables of the NSLP and SBP participation equations are presented in Table 2. Appendix Table A.2 provides mean values for these variables.
Table 2
Definition of Dependent and Explanatory Variables for the NSLP and SBP Participa
tion Equations
Variable                              Definition
Dependent Variables
  NSLP participation                  Dummy variable indicating
                                       whether any household
                                       members participate in
                                       the NSLP during a typical
                                       week (1 = yes, 0 = no)
  SBP participation                   Dummy variable indicating
                                       whether any household
                                       members participate in
                                       the SBP during a typical
                                       week (1 = yes, 0 = no)
Explanatory Variables
  Total income                        Average weekly earned
                                       income and income from
                                       other sources (including
                                       assistance programs) for
                                       the past month ($)
  Potential NSLP benefit              NSLP only: Value of the
                                       household's potential
                                       weekly benefits from the
                                       NSLP, defined as the
                                       NSLP subsidy value per
                                       meal for the household)
                                       x (number of school-aged
                                       children in the
                                       household) x (5 meals
                                       per week) ($)
  Potential SBP benefit               SBP only: Value of the
                                       household's potential
                                       weekly benefits from the
                                       SBP, defined as the (SBP
                                       subsidy value per meal
                                       for the household) x
                                       (number of school-aged
                                       children in the
                                       household) x (5 meals
                                       per week) ($)
  Household size                      Number of members of the
                                       household
  Proportion of household members     Number of household
                                       members aged 6 to 13
                                       years divided by
                                       household size
  Proportion of household members     Number of household
   aged 14 to 17 years                 members aged 14 to 17
                                       years divided by
                                       household size
  Respondent in nonwhite              Dummy variable indicating
                                       whether the respondent
                                       is non-white (1 = yes,
                                       0 = no)
  Single household head               Dummy variable indicating
                                       whether the household is
                                       headed by a single
                                       individual (1 = yes, 0 = no)
  Meal planner completed college     NSLP only: Dummy variable
                                       indicating whether the
                                       meal planner, assumed to
                                       be the female head (or
                                       male head, if no female
                                       head present), completed
                                       college (1 = yes, 0 = no)
  Meal planner employed               Dummy variable indicating
                                       whether the meal
                                       planner, assumed to be
                                       the female head (or male
                                       head, if no female head
                                       head present), was
                                       employed
                                       during the previous
                                       week (1 = yes, 0 = no)
  Adult at home for breakfast         SBP only: Dummy variable
                                       indicating whether there
                                       is an adult at
                                       home during breakfast
                                       time or school days
                                       (1 = yes, 0 = no)
  Parent decides on meal              Dummy variable
                                       indicating whether the
                                       parent decides where the
                                       target
                                       child eats the meal on
                                       school days (1 = yes, 0 = no)
  Region: North Central, South, or    Dummy variables
                                       indicating whether the
                                       household is located in
                                       the
                                       North Central, South,
                                       or West region,
                                       respectively (1 = yes,
                                       0 = no)
Urban or suburban area                NSLP only: Dummy variable
                                       indicating whether the
                                       household is located
                                       in a nonrural area
                                       (1 = yes, 0 = no)
Urban area                            SBP only: Dummy
Suburban area                          variables indicating
                                       whether the household
                                       is located
                                       in urban area of a
                                       suburban area,
                                       respectively (1 = yes,
                                       0 = no)
Poverty status of school district     Dummy variables
Low level of poverty                   indicating whether the
Moderate level of poverty              level of poverty in the
                                       school
                                       district in which the
                                       household is located is
                                       low (0-11.9 percent of
                                       children below the
                                       poverty line) or
                                       moderate (12-24.9
                                       percent of the
                                       children below the
                                       poverty line),
                                       respectively (1 = yes,
                                       0 = no)
Constant                               Constant term


The measures of program participation used in this study are based on whether any member of the household participates in the relevant school nutrition program at least once during a typical week.(11) The explanatory variables included in the program participation equations are very similar to those of the food expenditure equation. As in that equation, I include measures of household resources, household size, and household composition, as well as variables reflecting the characteristics of the individual responsible for meal planning and preparation within the household.

Because bivariate probit is a complex maximum likelihood estimation procedure, obtaining parameter estimates can be difficult. In order to successfully estimate the NSLP/SBP bivariate probit model it was necessary to be relatively parsimonious in the model specification, particularly for NSLP participation where the majority of the sample was participating in the program. Consequently, some of the detailed variables in the food expenditure equation have been combined in one or both of the participation equations to form more general measures (e.g., "Earned income" and "Other cash income" are combined in a single "Total income" variable for the participation equations). And some variables that were not found to be significant in initial univariate probit models estimated for the sample with access to the program were excluded from the relevant participation equation (e.g., "Meal planner completed college" was excluded from the SBP participation equation).(12)

The participation equations also include measures that are intended to capture the household's preferences for meals at school. Those variables are: measures of the presence of the school-age children in the household, a measure indicating the presence of an adult at home during breakfast meal time on school days, and a measure indicating whether the parent decides where the target child eats on school days. Finally, a measure of the potential benefits that the household could receive if it chose to participate in the NSLP is included in the NSLP participation equation and a measure of potential SBP benefits is included in the SBP participation equation.(13) The latter variables in particular address an important consideration in the specification of the program participation equations - the conditions needed to identify the effect of program participation independent of food expenditure behavior. In particular, there is no conceptual basis for believing that the potential program benefits affect food expenditures; however, there is a strong basis for believing that such potential benefits do affect the participation decision. It is worth noting that the estimates of program impacts obtained from the food expenditure equation are not sensitive to marginal changes in the set of variables selected to identify the model.

C. The Estimation Results

As noted above, the focus of the analysis is on obtaining estimates of the impact of the programs on food expenditures for those households that have the programs available. Thus, this discussion focuses on the estimation of the food expenditure equation. The results of the estimation of the two school nutrition program participation equations are presented in Appendix Table A.3.

1. Program Impacts

The results of the analysis of food expenditures for households are presented in Table 3. The coefficient estimate for the NSLP subsidy suggests that each additional dollar of NSLP benefits reduces normal household food expenditures by about 61 cents.(14) This implies that less than one-half of the NSLP subsidy is used by the households to supplement normal food expenditures.

In contrast, the coefficient estimate for the SBP benefit is 0.357, although the estimate is not significantly different from zero in a statistical sense.(15) Nevertheless, the point estimate of .357 implies that household food expenditures increase by more than one dollar for each additional

(10.) It is important to control for out-of-the-ordinary events since the goal of the analysis is to examine the impact of the NSLP and the SBP programs on usual food expenditures. Nineteen percent of the households reported spending "a lot more" on food during the past week than they normally spend in a week, while 35 percent reported spending "a lot less." Unfortunately, the households were not asked to explain why their food expenditures during the past week were unusually high or low. However, data from the Nationwide Food Consumption Survey on frequency of major food shopping trips suggests that infrequent shopping trips may be an important factor since many households undertake such shopping trips on a biweekly or monthly basis. The coefficient estimates for the program benefit variables and for the majority of the other variables in the model are virtually unchanged with the inclusion of the unusual expenditure variables. (11.) Because of problems with missing data on program participation for children in the household other than the sample target child, it was not possible to define the participation variables for the same time period as was used for the food expenditure measure (i.e., the previous week). It is likely that the relationship between school nutrition program participation in a typical week and household food expenditures during the prior week is less strong than the relationship between program participation and food expenditures during the same week. (12.) In subsequent runs testing the sensitivity of the program impact estimates from the food expenditure equation to marginal changes in the specification of the bivarate probit model, the inclusion/exclusion of these variables had little impact on the program-impact estimates. (13.) Because of the strong collinearity of the two potential benefit variables, I did not include the value of the potential NSLP benefits in the SBP participation equation. (14.) Because of the definition of total food expenditures used in this study, the value of the marginal propensity to consume (MPC) for food out of the school nutrition program benefits is defined as one plus the relevant coefficient estimate. (15.) Given the large standard error for the coefficient estimate for the SBP benefits, it is not surprising that the impact of the SBP benefit is not significantly different from that for the NSLP benefit. dollar of SBP benefits. Such super-supplementation of household food expenditures could reflect changes in household behavior in response to the SBP, for example, an increased likelihood that SBP-participant children eat any breakfast. Evidence on this issue is mixed. Wellisch et al. (1983a,b) found that a minor nutritional benefit of the SBP is a higher likelihood that a student would eat any breakfast, while Devaney et al. (1986) found no evidence of an impact of the SBP on the probability of eating breakfast.

It appears that the food expenditures of the households are not reduced by SBP benefits; rather, the SBP subsidy acts as a complete supplement to the households' normal food expenditures and may encourage an increase in food expenditures in excess of the value of the program benefits.

A finding of complete supplementation of food expenditures by SBP benefits is consistent with the results obtained by Wellisch et al. (1983a,b), while the finding of some substitution of food expenditures by NSLP benefits is quite different from their finding of complete supplementation. However, the estimate of 39 cents out of every dollar of NSLP subsidy supplementing household food expenditures is comparable to the estimate of .60 reported in the study of West and Price (1976).

Although estimates of the impact of WIC and FSP benefits on food expenditures can be obtained from this study, care should be taken in the interpretation of such estimates. Since the NESNP-1 sample population does not correspond to either the WIC-eligible or FSP-eligible populations, the coefficient estimates obtained for those programs should not be interpreted as measures of the impacts of the programs on their respective target populations. Rather, the coefficient estimates reflect the impacts of the FSP and WIC on the population of households with the NSLP available. Furthermore, the adjustment for possible selection bias due to program participation decisions has been limited to the programs of interest in this study - the NSLP and the SBP. No effort has been made to purge the estimates of the impact of the FSP and WIC on food expenditures of such selection bias.[16]

2. Other Findings

In addition to estimating the effects of the benefits from the school nutrition programs on food expenditures, the impacts of earned income and other cash income (including public assistance/welfare) on the household's food expenditures are derived. As can be seen in Table 3, the proportions of each additional dollar of earned income and unearned income allocated to food expenditures are .04 and .02 respectively, for the households with access to the NSLP only. For the households with access to both the NSLP and SBP, the estimated proportions for earned and unearned income are both about .06.[17]
Table 3
Estimation Results for Total Household Food Expenditures, Fall
1980
(weighted)
                                      Coefficient   Standard
Explanatory Variables                  Estimate       Error
Earned income                            .037**        .003
Earned income x SBP availability         .020**        .005
Other cash income                        .016**        .003
Other cash income x SBP availability     .039**        .009
NSLP benefit                            -.607**        .171
SBP benefits                             .357          .497
FSP benefits                            -.125          .069
WIC benefits                            -.373          .405
Ate home grown food                    -3.752**        .412
Expenditures unusually high             6.269          .480
Expenditures unusually low             -6.898**        .400
Household size in AME                  -1.609**        -53
Respondent is Black                    -1.565**        .591
Respondent is Hispanic                  -.763          .693
Single head of household                1.190*         .596
Meal planner aged 35 years or more       .829*         .398
Meal planner completed high school      -.533          .464
Meal planner completed college         -2.799**        .684
Meal planner employed                   -.309          .386
Region
  North Central                        -1.623*         .630
  North Central x SBP availability     -4.996**       1.240
  West                                 -3.722**        .761
  West X SBP availability               -.870         1.097
  South                                -1.480*         .679
  South X SBP availability             -3.413          .886
Urban area                              1.757          .617
Urban area X SBP availability          -2.425          .948
Suburban area                            .029          .647
Suburban area X SBP availability        1.524         1.059
Poverty status of school district
  Low level of poverty                 -1.780*         .836
  Low level X SBP availability          1.261         1.066
  Moderate level of poverty            -1.584          .880
  Moderate level X SBP availability     4.203**       1.068
Selection-bias correction terms
  NSLP participation                     .983*         .467
  SBP participation                     1.226**        .394
Constant                               35.461**       1.182
Chi-squared (df)                    1,681.5 (35)
Sample size                           5,778
Mean of dependent variable            27,455
Source: Data are from the National Evaluation of School Nutrition Programs-I, Fa
ll
1980.
* Significant at the .05 level, two-tailed test.
** Significant at the .01 level, two-tailed test.


Other findings of interest include the effect of socioeconomic characteristics of the household and characteristics of the household's meal planner on food expenditures. As reported in Table 3, food expenditures per AME are significantly lower of households that consumed home grown food during the past week and for larger households, all else equal. Since food expenditures are measured on a per household member basis,the latter finding reflects the presence of economic of scale in the purchase and preparation of food products.

Households in which the survey respondent is black and households with better educated meal planners have lower food expenditures, while households headed by a single parent and households with older meal planners have higher food expenditures, all else equal. The lower spending on food per adult-made-equivalent household member by the better educated meal planners may reflect efficient food purchase (under the assumption that the AME adjustment is an appropriate scaling for household size).

Somewhat surprisingly, the employment status of the meal planner does not have a significant impact on household food expenditures, after controlling for the impact of earnings on those purchases.(18) One might expect that food expenditures would be higher for households in which the meal planner was employed because of a greater use of more expensive convenience foods and food away from home relative to households in which the meal planner does not work. That hypothesis is not supported by our findings.

Finally, the significance of the coefficients for the selection-bias correction terms indicate the presence of systematic differences in the food expenditures of program participants and nonparticipants that are controlled through the two-stage estimations procedure.

V. Summary and Conclusions

In this study, the extend to which the school nutrition programs supplement the normal food expenditures of households that have access to the NSLP and the SBP is examined. The results that are obtained from the estimation of the food expenditure equation indicate that somewhat less than one-half of each additional dollar of NSLP benefits is used by the households to supplement food expenditures, while all of each additional dollar of SBP benefits is allocated to households food expenditures. The finding that there is some substitution of food expenditures by the NSLP benefits and complete supplementation of food expenditures by the SBP benefits, suggest that school nutritional program benefits do supplement the food expenditures of the households. Furthermore, the benefits that are targeted through the SBP provide for greater supplementation of household food expenditures, perhaps because of changes in household behavior in response to the program (such as an increased probability that children eat breakfast).
Table A1
Mean Values for the Explanatory Variables that are
Included in the Total Household Food Expenditures
Equation, Fall 1980 (weighted)
                                                  Standard
Explanatory Variable                      Mean       Error
Earned income                           $98.01       80.60
Earned income x SBP availability        $37.53       65.33
Other cash income                       $21.23       58.85
Other cash income x SBP availability    $ 7.86       25.08
NSLP benefit                            $ 1.54        1.54
SBP benefit                             $ 0.19         .52
FSP benefit                             $ 1.06        3.20
WIC benefit                             $ 0.06         .45
Ate home grown food                        .33         .47
Expenditures unusually high                .19         .40
Expenditures unusually low                 .35         .48
Household size in AME                     4.06        1.37
Respondent is Black                        .16         .37
Respondent is Hispanic                     .09         .29
Single head of household                   .18         .39
Meal  planner aged 35 years or more        .66         .48
Meal planner completed high school         .62         .49
Meal planner completed college             .12         .33
Meal planner employed                      .55         .50
North Central                              .23         .42
North Central x SBP availability           .04         .20
West                                       .18         .39
West x SBP availability                    .09         .29
South                                      .38         .49
South x SBP availability                   .23         .42
Urban area                                 .39         .49
Urban area x SBP availability              .19         .39
Suburban area                              .30         .46
Suburban area x SBP availability           .14         .34
Low level of poverty                       .51         .50
Low level x SBP availability               .14         .35
Moderate level of poverty                  .35         .48
Moderate level x SBP availability          .21         .40
Constant                                  1.00         .00
Sample size                              5,778
Source: Data are from the National Evaluation of School Nutrition
Programs-I, Fall 1980


[TABULAR DATA OMITTED]
Table A3
Estimation Results for the Bivariate Probit Model of NSLP and SBP
Participation for Households with Access to the NSLP and the SBP,
Fall 1980 (weighted; standard errors in parentheses)
                                    Coefficient Estimates for
                                 NSLP                     SBP
Explanatory Variables           Participation         Participation
Total income                       -.0002                 -.0004(*)
                                   (.0003)                (.0001)
Potential NSLP benefit             -.123(**)                 --
                                   (.041)
Potential SBP benefit               --                     .134(**)
                                                          (.117)
Household size                     -.104                  -.047
                                   (.816)                 (.253)
Proportion household members       -.484                   .065
  aged 6 to 13 years               (.681)                 (.223)
Proportion household members        .173                  -.782(**)
  aged 14 to 17 years              (.796)                 (.232)
Respondent is nonwhite              .115                   .407(**)
                                   (.244)                 (.065)
Single household head              -.482                   .103
                                   (.253)                 (.083)
Meal planner completed college     -.517(*)                 --
                                   (.208)
Meal planner employed              -.071                   .134(*)
                                   (.174)                 (.059)
Adult at home for breakfast         --                    -.393(**)
                                                          (.107)
Parents decide on meal              .089                  -.482(**)
                                   (.178)                 (.057)
Region
  North Central                     .484                   .320(**)
                                   (.342)                (1.118)
  West                              .107                   .005
                                   (.311)                 (.097)
  South                             .237                  -.018
                                   (.266)                 (.098)
Urban or suburban area             -.474(*)                 --
                                  -(.236)
Urban area                           --                   -.670(**)
    (.080)
Suburban area                        --                   -.860(**)
                                                          (.096)
Poverty status of school district
  Low level of poverty              .639(*)                .188(*)
                                   (.270)                 (.095)
  Moderate level of poverty         .110                  -.138
                                   (.211)                 (.082)
Constant                           2.173(**)               .958(**)
                                   (.462)                 (.208)
Rho                                             .523(**)
                                               (.209)
Chi-squared (df)                             878.40 (37)
Sample size                                2,710
Source: Data are from the National Evaluation of School Nutrition Programs-I, Fa
ll
1980.
Note: These equations were estimated for the sample of households with both the
NSLP
and SBP available using bivariate probit.
(*) Significant at the .05 level, two-tailed test.
(**) Significant at the .01 level, two-tailed test.
Table A4
Estimation Results for the Univariate Probit Model of
NSLP Participation for Households with Access to the
NSLP Only, Fall 1980 (weighted; standard errors in
parentheses)
Explanatory Variable             Coefficient Estimate
Total income                           .0002
                                      (.0001)
Potential NSLP benefits                .117(**)
                                      (.029)
Household size                        -.091(*)
                                      (.039)
Proportion of household members       -.387
  aged 6 to 13 years                  (.398)
Proportion of household members        .665
  aged 14 to 17 years                 (.440)
Respondent is nonwhite                 .399
                                      (.204)
Single household head                  .154
                                      (.171)
Meal planner completed college        -.120
                                      (.114)
Meal planner employed                 (.041)
                                      (.092)
Parent decides on meal                -.014
                                      (.094)
Region
  North Central                        .238
                                      (.123)
  West                                 .042
                                      (.137)
  South                               -.164
                                      (.130)
Urban or suburban area                -.955(**)
                                      (.141)
School district poverty status
  Low poverty                         -.311
                                      (.248)
  Moderate poverty                    -.036
                                      (.279)
Constant                              2.615(**)
                                      (.353)
Chi-squared (df)                    107.60 (16)
Sample size                            3,068
Mean of dependent variable             .956
Source: Data are from the National Evaluation of School Nutrition
Programs-I, Fall 1980.
(*) Significant at the .05 level, two-tailed test.
(**) Significant at the 0.01 level, two-tailed test.


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Author:Long, Sharon K.
Publication:Journal of Human Resources
Date:Sep 22, 1991
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