Our results also demonstrate that models that gauge a housing bubble by comparing movements in housing price indexes with movements in other indexes or with the values predicted by regression models are flawed, because they assume that market prices fluctuate randomly around fundamental values. Those models must assume that prices were close to fundamentals in the past in order to conclude that the 2001–05 run-up pushed prices above fundamentals. But maybe prices were below fundamentals in the past and the 2001–05 run-up pushed prices closer to fundamentals.
Brookings Institution
Winter 2006