You have to take the much longer view when you talk about the merits of investing pensions or SS in stocks. The compounding affects of a broad S&P portfolio will destroy an all bond portfolio in a 20-30 time frame.

And now that we are printing all this money and have massive unfunded liabilities, there will be serious inflation in the next 20 years - I have no idea when, but bond yields will drop or become negative at some point while equities will perform much better. And this is Charlie Munger and Warren Buffett's view as well.