While other people expect home prices to bounce along the bottom for a while without going up much, Robert Shiller is inclined to be more pessimistic. There is room for home prices to decline another 10% to 25% in real terms over the next five years, according to Shiller. Speaking at a Standard & Poor’s Housing Summit in New York on Thursday, the Yale University professor and co-founder of the S&P Case-Shiller Home Price Indices, noted that the current downturn is the biggest ever in U.S. history in terms of the peak to trough housing price collapse. After adjusting for inflation, home prices were not down so much even during the Great Depression, according to Shiller. About half of all mortgage debt was in default during the Great Depression, according to HousingWire research. By 1932, national unemployment reached up to 25% according to the Kansas Department of Labor. The Federal Deposit Insurance Corp. estimates about 9,000 banks suspended operations, resulting in losses to depositors of about $1.3 billion. Annual mortgage lending fell 80% and new residential construction had dropped by 80% as well. The National Association of Home Builders’ traffic of prospective buyers index peaked in 2005, two or three years before the financial collapse. After that, “It seems like someone blew a whistle that only dogs and homebuyers could hear,” which led the index to drop from there. Going by the S&P Home Price Indices, the downturn bottomed out in 2009, as the effects of the government tax credit started to be felt, but the index is likely to confirm a double dip in home prices next month, according to Shiller. Part of the downturn is seasonal and the index could turn back up again in the summer months. As Shiller sees it, the economy is at a tipping point, with the unemployment rate and housing showing declines again, which might suggest another recession. Poonka Thangavelu is a HousingWire contributor based in New York.