Here's a new theory I have been working on: there is a much higher correlation between the availability of credit and housing appreciation than there is between jobs or population growth.
If this theory of mine is true, then a contraction in credit will negatively impact real-estate more than either job losses or population declines. If true, this theory would also imply that the best way to determine how far prices will rise and decline is to track the availability of credit.
This is the big question. How can we track credit availability? I know there are statistics to show the money supply for the US, but that is such an aggregate number that it hard to parse how much is from JUST credit, and mortgages specifically. Worse, I have no idea how one would look at this from a regional level, like a particular city.
If the credit markets are national then maybe this doesn't really matter. I suspect that this hasn't always been the case. Back in the '60s and '70s I think that banks operated much more on a "local" level, and that they were more responsive to local conditions than global investor interest in mortgage securities, thus the national money supply stats might be useful for trending against real-estate prices in recent years, but might not be relevant for past years.
Maybe trend data for the types of mortgages offered (e.g. negative amortization, 100% finance, 30 year fixed, etc) might be a good proxy for the credit availability in particular regions. If my theory holds, then the periods with the greatest house appreciation would also be those with the largest proportion of "easy" mortgage types.
Oh well, proving my theory is likely just a pipe dream. I doubt that such historical data on trends of mortgage types even exists, and certainly not on a local or regional level.