A quickie then. Figure that the average person spends 45 years working and 15 years in retirement. The average retirement fund money is in the market for 30 years.
Pick any 30 years on this chart. This is the Dow Jones industrial average, a set of average stocks that is often tracked. We are now at the bottom of a very volatile market, so hell, pick the last 30 years if you like. This is the average retirement investment. If people cash out now, completely, they are only going to make a small fortune and not a huge one. If they can hold off cashing out big for 4-5 years it will be a huge fortune again.
This chart does not even include the results of reinvestment of earnings, compounding interest or making smarter than average investments. My momma, for example, took all her retirement funds out of the market in 2007, because she is a brilliant investor.