Yale economist Robert Shiller, who called both the Internet and housing busts, says that he doesn’t see another era of “irrational exuberance” occurring anytime soon. But that doesn’t mean he’s not concerned about both the stock market and housing market.

“Given the economic situation, I’m worried about the stock market — both of them, stock and housing market,” Shiller tells Yahoo! TechTicker. “These booms we’re seeing now can’t be trusted to continue.” Shiller says the stock market is currently overvalued, with his 10-year price/earnings ratio now close to 20. (Its historical average is about 15.) But Shiller adds that that doesn’t mean people should be out of stocks. Throughout history, stocks have often continued to climb when 10-year P/Es have hit current levels, he says. As for another bubble forming, Shiller doesn’t see it right now. “During a real boom it becomes a whole culture … where we are all starry eyed optimists,” he says. “I just don’t see that coming back in this environment.”