This could be due to measurement error – and perhaps inflation (de-valuing of the dollar) really is that bad:

Rosenberg: Historically, home prices go up one- to two percentage points above the inflation rate. Right now it’s going up 12 percentage points. Residential real estate is a great hedge against inflation. But the excess is practically unprecedented.

Source: Prepare for a recession this summer, a bear market in real estate and a drop in stock prices, warns strategist David Rosenberg – MarketWatch