This paper has developed alternative approaches for projecting the long-term Social Security real interest rate, including an examination of historical data and estimation of yield curves for the Treasury inflation-indexed market. The examination of historical experience back through 1870 implies that the long-term real interest rate is near 3 percent. Forward-looking projections from yield curves for inflation-indexed Treasuries for the past three years have averaged about 2.8 percent.
But currently, the real rate on TIPS is around 2 percent. I don't care what the average was over the past three years. Would the Treasury like to offer me foreign exchange trades at the average exchange rate over the past three years?
As long as government operates under the assumption that the real interest rate on Social Security is higher than the rate on TIPS, the math on privatization is going to look bad.