Gap = (Actual Index Level - Mean Pre-Bubble Ratio) / Actual Index Level

The ratio of the S&P/Case-Shiller Home Price Index Level to U.S. GDP Nominal Dollars (SAAR) . The U.S. GDP index is based upon data reported by The Bureau of Economic Analysis. The U.S. Home Price-to-GDP Gap is the percentage difference between the current level of the ratio and the mean, pre-bubble ratio. The pre-bubble mean ratio is derived by from data from 1987 through 1999.