If you're thinking about selling your home because you think the housing market is on the mend, MIT professor William Wheaton says maybe you should think again. He says we'll be slogging on the bottom for some time to come. Now, he suggests, we're just establishing an equilibrium between renting and owning. NPR's Robert Siegel talks to Wheaton, who is a professor of economics and urban studies and planning at the MIT Center for Real Estate, about the lackluster -- even dreary -- housing forecast.