<snip>
He recorded all the payroll taxes he paid into the system (including the matching amount from his employer), tracked down the return the Social Security Trust Fund earned for each of the 45 years, and then compared the result with what he would have gotten had he been able to invest the same amount of payroll tax money over the same period in the Dow Jones Industrial Average (including dividends).
To his surprise, the Social Security investment won out: $261,372 versus $255,499, a difference of $5,873.
</snip>
http://www.csmonitor.com/2004/1227/p01s03-cogn.html