When the earnings yield of stocks is much higher than bond yield

Earnings yield spread – The earnings yield of a company is the earnings divided by the price of the stock. When the earnings yield of stocks is much higher than bond yields (the spread), historically it has been a good indicator of future stock performance.

http://www.skyig.com/pdf/q305_newsletter.pdf

http://www.ifaonline.co.uk/public/showPage.html?page=ifa2006_articleimport&tempPageName=862245