As of the close Friday, the S&P 500 is down 39% from the highs set last October.  If you held stocks at that time, you are down 39%.

To get back to that level, the market would have to rise 63%. 

On any given trading day, how often has the stock market gone up 63% one year later?

There have been 20,291 trading days since December 30, 1927.  On only 145 occasions did the S&P 500 rise 63% a year later, or 0.7% of the time.

And when was the last time the market rose 63% or more in one year? 

October 18, 1935.

In fact, the only times when the S&P 500 rose 63% a year after any given trading day occurred between May 13, 1932 and October 18, 1935. 

There has been more success over two years.  In 4.4% of the instances, stocks have been up 63% or more two years later. 

This last occurred from 1996 through 1998.  The prior 63% move over two years ended in 1987, before the crash.  It also happened in 1976 as the market soared off the 1974 lows, in 1955-56 and in the 1930s.

This does not necessarily mean you should liquidate your portfolio now.  However, one should not be fully invested in stocks all the time.  Last year was one of those times.