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  • Is There a Bubble in the Housing Market?
  • Karl E. Case and Robert J. Shiller

The popular press is full of speculation that the United States, as well as other countries, is in a “housing bubble” that is about to burst. Barrons, Money magazine, and The Economist have all run recent feature stories about the irrational run-up in home prices and the potential for a crash. The Economist has published a series of articles with titles like “Castles in Hot Air,” “House of Cards,” “Bubble Trouble,” and “Betting the House.” These accounts have necessarily raised concerns among the general public. But how do we know if the housing market is in a bubble?

The term “bubble” is widely used but rarely clearly defined. We believe that in its widespread use the term refers to a situation in which excessive public expectations of future price increases cause prices to be temporarily elevated. During a housing price bubble, homebuyers think that a home that they would normally consider too expensive for them is now an acceptable purchase because they will be compensated by significant further price increases. They will not need to save as much as they otherwise might, because they expect the increased value of their home to do the saving for them. First-time homebuyers may also worry during a housing bubble that if they do not buy now, they will not be able to afford a home later. Furthermore, the expectation of large price increases may have a strong impact on demand if people think that home prices are very unlikely to fall, and certainly not likely to fall for long, so that there is little perceived risk associated with an investment in a home. [End Page 299]

If expectations of rapid and steady future price increases are important motivating factors for buyers, then home prices are inherently unstable. Prices cannot go up rapidly forever, and when people perceive that prices have stopped going up, this support for their acceptance of high home prices could break down. Prices could then fall as a result of diminished demand: the bubble bursts.

At least one aspect of a housing bubble—the rapid price increases—has clearly been seen recently. A rapid surge in home prices after 2000, as tabulated, for example, by the Economist Intelligence Service, has been seen in almost all the advanced economies of the world, with the exception of Germany and Japan. In some of these countries, price-to-rental ratios and price-to-average income ratios are at levels not seen since their data begin in 1975.1

But the mere fact of rapid price increases is not in itself conclusive evidence of a bubble. The basic questions that still must be answered are whether expectations of large future price increases are sustaining the market, whether these expectations are salient enough to generate anxieties among potential homebuyers, and whether there is sufficient confidence in such expectations to motivate action.

In addition, changes in fundamentals may explain much of the increase. As we will show, income growth alone explains the pattern of recent home price increases in most states. Falling interest rates clearly explain much of the recent run-up nationally; they can also explain some of the cross-state variation in appreciation because of differences in the elasticities of supply of homes, including land.

To shed light on whether the current boom is a bubble and whether it is likely to burst or deflate, we present two pieces of new evidence. First, we analyze U.S. state-level data on home prices and the “fundamentals,” including income, over a period of seventy-one quarters from 1985 to 2002.

Second, we present the results of a new questionnaire survey conducted in 2003 of people who bought homes in 2002 in four metropolitan areas: Los Angeles, San Francisco, Boston, and Milwaukee. The survey replicates one we did in these same metropolitan areas in 1988, during another purported housing bubble, after which prices did indeed fall sharply in many cities. The results of the new survey thus allow comparison [End Page 300] of the present situation with that one. Our survey also allows us to compare metropolitan areas...


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pp. 299-362
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