Seasonal Stock Market Rationale for "SELL in May and Go Away" (until November)...

The 6-month period from November-April has gained +548.3% for the S&P 500 since 1990, 8 ½ times the +65.1% return achieved during the 6 months from May-October.

Both numbers are aggregate total return performance results calculated for their respective 6-month periods beginning on 05/01/90 and continuing through 04/30/15. 

Source: BTN Research