That’s how far prices on Chicago’s least expensive homes­ (the bottom third of the local housing stock, selling for less than $143,616) had fallen from their March 2007 peak through February 2012, according to the Standard & Poor’s/Case-Shiller Home Price Indices. By contrast, the top third—homes selling for more than $244,611—lost only 31 percent of their peak value, and the middle rank ($143,616 to $244,611) lost 43 percent.