Even as the new Case-Shiller report shows that house prices rose a little in August, James Kwak and Simon Johnson show in the Washington Post how propping up home prices via tax incentives is like ingesting crack or heroin -- you have to keep taking bigger and bigger doses to get the the same high. (HT Calculated Risk.)

What happens when you artificially prop up housing prices? Imagine the credit were expanded to all home buyers and made permanent. This would simply boost housing prices at the low end of the market by close to $8,000, since all buyers would be willing to pay $8,000 more. (Prices would rise by a little less than $8,000 because at higher prices, more people would be willing to sell.) Whom does this benefit? Not first-time home buyers. It benefits people who already own houses (and their real estate agents) because it's a one-time boost in housing values.

This would be just the latest chapter in a long history of government policies to boost housing prices -- the mortgage interest tax deduction, the capital gains exclusion on houses, the extension of the mortgage interest tax deduction to second houses, etc. Each of these policies pushes up prices just once; if you want to keep pushing up housing prices, you have to keep adding sweeteners.