Alan Greenspan's comments on housing market in June 9 testimony before Congress

The housing market in the United States is quite heterogeneous, and it does not have the capacity to move excesses easily from one area to another. Instead, we have a collection of only loosely connected local markets. Thus, while investors can arbitrage the price of a commodity such as aluminum between Portland, Maine, and Portland, Oregon, they cannot do that with home prices because they cannot move the houses. As a consequence, unlike the behavior of commodity prices, which varies little from place to place, the behavior of home prices varies widely across the nation.

Speculation in homes is largely local, especially for owner-occupied residences. For homeowners to realize accumulated capital gains on a residence--a precondition of a speculative market--they must move. Another formidable barrier to the emergence of speculative activity in housing markets is that home sales involve significant commissions and closing costs, which average in the neighborhood of 10 percent of the sales price. Where homeowner sales predominate, speculative turnover of homes is difficult.

But in recent years, the pace of turnover of existing homes has quickened. It appears that a substantial part of the acceleration in turnover reflects the purchase of second homes--either for investment or vacation purposes. Transactions in second homes, of course, are not restrained by the same forces that restrict the purchases or sales of primary residences--an individual can sell without having to move. This suggests that speculative activity may have had a greater role in generating the recent price increases than it has customarily had in the past.

The apparent froth in housing markets may have spilled over into mortgage markets. The dramatic increase in the prevalence of interest-only loans, as well as the introduction of other relatively exotic forms of adjustable-rate mortgages, are developments of particular concern. To be sure, these financing vehicles have their appropriate uses. But to the extent that some households may be employing these instruments to purchase a home that would otherwise be unaffordable, their use is beginning to add to the pressures in the marketplace.

The U.S. economy has weathered such episodes before without experiencing significant declines in the national average level of home prices. In part, this is explained by an underlying uptrend in home prices. Because of the degree of customization of homes, it is difficult to achieve significant productivity gains in residential building despite the ongoing technological advances in other areas of our economy. As a result, productivity gains in residential construction have lagged behind the average productivity increases in the United States for many decades. This shortfall has been one of the reasons that house prices have consistently outpaced the general price level for many decades.