Bubbling up.

"There can be little doubt that exceptionally low interest rates on 10-year Treasury notes, and hence on home mortgages, have been a major factor in the recent surge of homebuilding and home turnover, and especially in the steep climb in home prices. Although a 'bubble' in home prices for the nation as a whole does not appear likely, there do appear to be, at a minimum, signs of froth in some local markets where home prices seem to have risen to unsustainable levels.

"Although we certainly cannot rule out home price declines, especially in some local markets, these declines, were they to occur, likely would not have substantial macroeconomic implications. Nationwide banking and widespread securitization of mortgages make it less likely that financial intermediation would be impaired than was the case in prior episodes of regional house price corrections. Moreover, a substantial rise in bankruptcies would require a quite-significant overall reduction in the national housing price level because the vast majority of homeowners have built up substantial equity in their homes despite large home equity withdrawals in recent years financed by the mortgage market."

Alan Greenspan, June 9 testimony to the Joint Economic Committee of Congress