On the one hand, it seems obvious; didn’t we all know there was a housing bubble back in 2006? On the other hand, if it’s that easy, why aren’t we all as rich as John Paulson?
A while back I suggested that the Fed could spot a housing bubble by treating housing prices the same way if treats the prices that make up the CPI. If there is high inflation in the core CPI, you don’t stop and ask if there is a fundamental reason for higher inflation; you tighten monetary policy (raise interest rates). The Fed could do the same thing for housing prices, since housing is an asset that people need to consume. But that’s probably a simplistic view.
Leigh Caldwell thinks that behavioral approaches may be able to separate out irrational overvaluation from changes in fundamental values. I believe his argument is that you can measure the degree of irrational overvaluation for certain types of assets, and you can extrapolate from there to see if there is a bubble:
Outside of the laboratory, precise knowledge of the returns of some assets does become available at times, and it would be possible to measure investors’ behaviour with regard to those assets. If investors, in aggregate, become overconfident about returns it will be possible to spot this from certain types of price change.