Experts agree that the best and cheapest way to assure a lifetime income is "buying" the equivalent of an annuity from Social Security by delaying a claim for retirement benefits, writes Alicia Munnell. "But why not go beyond allowing people to increase their annuity income by delaying claiming, and let people purchase annuities outright from Social Security?" she writes. "Yes, that's right. Put Social Security in the annuity business."