Forecasting home prices is impossible because there's no historical precedent for the real estate bubble of the 2000s and the subsequent price drop, Shiller said.
"In real terms, there has never been a bust of this proportion," he said. "Even in the Great Depression, home prices fell nominally approximately almost as much as they did recently. But that was with all prices falling. So real estate prices didn't go down hardly at all during the Depression."