Private social security accounts

Cato's William Shipman and Peter Ferrara argue that, despite the threat of major downturns in the financial markets, private social security accounts are still the way to go:

Suppose a senior citizen — let's call him "Joe the Plumber" — who retired at the end of 2009, at age 66, had been able to set up a personal account when he entered the work force in 1965, at the age of 21. Suppose that, paying into his personal account what he and his employer would have paid into Social Security, Joe was foolish enough to invest his entire portfolio in the stock market for all 45 years of his working career. How would he have fared in the recent financial crisis?

While working, Joe had earned the average income for full-time male workers. His wife Mary, also age 66, had earned the average income for full-time female workers. They invested together in an indexed portfolio of 90% large-cap stocks and 10% small-cap stocks, which earned the returns reported each year since 1965.

By the time of their retirement in 2009, Joe and Mary would have accumulated account funds, after administrative costs, of $855,175. Indeed, they would have been millionaires a few years earlier, but the financial crisis lost them 37% in 2008. They were unfortunate to retire just one year after the worst 10-year stock market performance since 1926. Yet their account, having earned a 6.75% return annually from 1965 to 2009, would still pay them about 75% more than Social Security would have.