Prof Shiller added there was no historical evidence for a link between interest rates and share prices. "You would think that when interest rates are higher people would sell stocks, but the financial world just isn't that simple."
He defended his now famous measure of valuation, often referred to as the Cape (for cyclically adjusted price/earnings multiple), which compares share prices to average earnings over the previous 10 years. This adjusts for the cyclicality of earnings.
The indicator showed stocks were seriously overvalued before the market peaks of 2000 and 2007 — but it has also suggested stocks have been overpriced for the past several years, while prices have continued to rise. That prompted several attacks on the Cape, saying it did not take account of changing accounting and tax rules over time, and it was distorted by the sharp fall in earnings that followed the Lehman Brothers bankruptcy in 2008.
Mr Shiller pointed out the fall in earnings in 2008 came as part of a severe recession. "Companies like to take write-offs right away during a recession. Then their earnings can recover from there. If I average over 10 years I don't see that as a problem. The average includes the actual losses that companies have made."