BOB MOON: Too many unsold homes, and not enough willing or able buyers. That’s the painful story in this morning’s latest Case-Shiller home-price index. It shows home prices have relapsed to the same levels they were when the housing bubble popped back in 2006.

On the line with us is Chris Mayer. He’s a professor of real estate at the Columbia Business School. Good morning.

CHRIS MAYER: Good morning Bob.

MOON: This seems like two steps forward, two steps back. Home prices down yet another month. How can we get a solid recovery when the housing sector just refuses to budge here?

MAYER: The good news so to speak is that things can’t get a lot worse, but you know, in terms of the overall macro economy we’re already building so few homes that it’s not going to make the employment situation worse than it is.

MOON: Well, how much longer though can our economy sustain these kinds of numbers?

MAYER: I do think that if we continue to see house prices fall, the real risks are that homeowners are going to stop making their mortgage payments, lenders are going to get into trouble again. I don’t think we’re likely to see that at the pace we’re going, but we’re certainly not going to see much of a recovery.

MOON: Do you think it’s possible that home owners are going to start taking strategic defaults because they just don’t see a way out?

MAYER: This is the million-dollar, trillion-dollar question. So far, strategic defaults have remained as significant but not a dominant force. If they start becoming a dominant force in the housing market then everything changes. And the more prices fall, the more risk there is that that happens.

MOON: Well, we can only keep hoping. Chris Mayer is a professor of real estate at the Columbia Business School. Thanks for joining us.

MAYER: Good to talk to you Bob.