The excess cash that has been loaned to the government was loaned on terms better than your private pension gets. So do you ever ask, how much of your private pension wasn't diverted for other purposes?
And how do you determine that? The interest rate on securities held by Social Security is determined on a monthly basis. Maybe you don't know as much as you claim to know.
Interest rates
Special-issue investments bear interest rates determined monthly by
a formula. An interest rate is determined on the last business day of a month and applies to securities issued in the following month. Tables of such
monthly interest rates provide rates back to 1937—the beginning of the Social Security program.
http://www.ssa.gov/OACT/ProgData/intRates.html
And here is a listing of the yearly interest rates Social Security has earned over it's lifetime. Not very impressive, considering my private retirement fund had interest rates as much as 14%, until Bush's great economy.
http://www.ssa.gov/OACT/ProgData/newIssueRates.html
And my private pension has administrative costs, which is a diversion of funds. As well the State of Michigan SERE retirement fund, has administrative costs; which were to the tune of $28+ million in 2013, so I wouldn't doubt Social Security incurs costs above and beyond expenditures incurred paying out benefits since the fund is required by law to be invested in non-marketable
securities issued and guaranteed by the "full faith and credit" of the federal government.