"At the peak of the boom in 2006, over a third of all U.S. home purchase lending was made to people who already owned at least one house. In the four states with the most pronounced housing cycles, the investor share was nearly half 45 percent. Investor shares roughly doubled between 2000 and 2006. While some of these loans went to borrowers with “just” two homes, the increase in percentage terms is largest among those owning three or more properties.