HOME prices in the United States have been falling for nearly three years, and the decline may well continue for some time.

Even the federal government has projected price decreases through 2010. As a baseline, the stress tests recently performed on big banks included a total fall in housing prices of 41 percent from 2006 through 2010. Their “more adverse” forecast projected a drop of 48 percent  suggesting that important housing ratios, like price to rent, and price to construction cost  would fall to their lowest levels in 20 years.

Such long, steady housing price declines seem to defy both common sense and the traditional laws of economics, which assume that people act rationally and that markets are efficient. Why would a sensible person watch the value of his home fall for years, only to sell for a big loss? Why not sell early in the cycle? If people acted as the efficient-market theory says they should, prices would come down right away, not gradually over years, and these cycles would be much shorter.

But something is definitely different about real estate. Long declines do happen with some regularity. And despite the uptick last week in pending home sales and recent improvement in consumer confidence, we still appear to be in a continuing price decline.