The CR Money Lab looked at a hypothetical employee we'll call Jack, born in October 1946. If Jack has reason to think he might not live to his full retirement age of 66, he'd be wise to start collecting as soon as he can and at least get something. But if he expects to live to 90 or beyond, he should try to wait until age 70 to collect. That's because 20 years of the $35,340 in annual benefits he'd get by waiting adds up to a much greater sum than 28 years of the $19,320 he'd accumulate by starting at 62. That's $709,745 vs. $542,570, in constant 2007 dollars. Note that this calculation ignores what you might earn if you started collecting early and invested the money, because of the unpredictability of investment returns and differences in individual circumstances.

Another way to look at it is in terms of Jack's break-even age. That's the point at which he would have collected the same amount whether he retired at 62 or 70. In Jack's case, that age is 79 years and 6 months. If he dies before that age, he'd have made a wise choice to take benefits early. If he lives beyond that, waiting to collect will give him more money overall. You can figure your own break-even age using the calculator at the Social Security Web site, at www.ssa.gov.