Largely for those reasons, economists have found that the impacts of the property wealth effect are well in excess of the impetus provided by the equity wealth effect. Whereas econometric studies demonstrate that consumers spend about 3-4 cents of every dollar's worth of equity appreciation, the spending propensity out of property appreciation is closer to 7 cents on the dollar (see Karl Case, John Quigley, and Robert Shiller, "Comparing Wealth Effects: The Stock Market versus the Housing Market," NBER Working Paper, October 2001). This differential wealth effect is very important for the asset economy in one other way - it underscores the critical role of debt as the means by which asset appreciation can be converted into purchasing power. In property markets, equity extraction and debt go hand in hand. The property wealth effect is a far more debt-intensive phenomenon than the equity wealth effect.