Real estate booms and busts can have far-reaching consequences. These booms are generally accompanied by fast credit growth and sharp increases in leverage, and when the bust comes, debt overhang and deleveraging spirals can threaten financial and macroeconomic stability. These dangers notwithstanding, the traditional policy approach to real estate booms has been one of “benign neglect”. This was based on two main premises. First, the belief that, as for other asset prices, it is extremely difficult to identify unsustainable real estate booms, or “bubbles” (sharp price increases not justified by fundamentals), in a timely manner. Second, the notion that the distortions associated with preventing a boom outweigh the costs of cleaning up after a bust. The recent crisis has challenged (at least the second of) these assumptions.