"As of yesterday my price earnings ratio ... was 26.3," said Shiller to This Is Money. "There's only three major occasions in US history back to 1881 when it was higher than that. One is 1929, the year of the crash. The other is 2000, which I call the peak of the millennium bubble, and it was also followed by a crash. And then 2007, which was also followed by a crash."