A U.S. housing-market revival may prove illusory and the threat of further weakness remains, said Robert Shiller, a professor at Yale University and co-creator of the S&P/Case-Shiller index of property values.

“The housing market has been declining for something like six years now, it could go on, that’s my worry,” Shiller told Tom Keene in a Bloomberg Television interview Thursday in Davos, Switzerland. “The short-term indicators are up now, it definitely looks better, but we saw that in 2009.”