Surveys indicate that workers way behind on retirement plans. (Life/Health: Marketplace).

Two recent studies suggest that the average U.S. worker isn't saving enough and may have to work longer or accept a lower standard of living in retirement.

In a survey by John Hancock Financial Services, workers with defined-contribution retirement plans said they are not on course to achieve the 75% of pre-retirement income needed to maintain their lifestyles. Respondents said they devote little time to managing investments and lack the knowledge to do so effectively.

Most respondents said they were likely to achieve only 50% to 60% of their pre-retirement income, including projected Social Security benefits, said survey author Wayne Gates.

As to why plan participants don't devote more time to retirement planning, Gates said the answer "could be as simple as human nature," which he said may be "the Achilles heel of the 401(k) system."

Meanwhile, a report by the Employee Benefit Research Institute said the inadequacy of retirees' income remains a public-policy concern. The institute, which used Census Bureau data released in February for its report, concluded that overall participation in any type of retirement and pension plan has been "relatively constant" since the 1980s, but that a larger percentage of participants are in defined-contribution plans--mostly salary-reduction or 401(k)-type plans. Vesting in these plans has substantially increased since the 1980s, said institute president and chief executive officer Dallas Salisbury.