Robert Shiller, an economics professor at Yale University and co-creator of the S&P/Case-Shiller home-price index, talks about U.S. home prices, and the outlook for the housing market and the economy.   The Case-Shiller index of property values in 20 cities fell 4 percent from April 2010, the biggest drop since November 2009. Shiller speaks with Carol Massar and Matt Miller on Bloomberg Television’s "Street Smart."