EFF/KRF: There is no evidence that market timing in response to economic events enhances expected returns. The market tends to lead economic activity. Stock prices tend to fall in advance of recessions and rise in advance of economic upturns. To time markets successfully, you have to come up with better forecasts of economic activity than those already built into stock prices. We don't know anyone who can do this.
Moreover, investors who try to time the market by selling after news of a recession is already in prices are probably reducing their expected returns. Although realized returns are too volatile to make strong statements, there is some evidence that expected stock returns are relatively high during recessions and low during expansions. One can avoid the higher risk of stocks during recessions, but apparently only by passing up higher expected returns.
Eugene Fama and Ken French are members of the Board of Directors for and provide consulting services to Dimensional Fund Advisors LP.