About life expectancy.

At birth, average life expectancy is about 78 years (75 for men and 81 for women), according to the National Center for Health Statistics. However, if you are lucky enough to reach age 65, your average life expectancy rises to 82 for men and 85 for women. Remember, too, that the average is just that—you might be among those who live longer, in which case you would be glad you waited for a larger benefit.

Your break-even point.

At what age will you break even and begin to come out ahead if you delay Social Security? The break-even age depends on the amount of your benefits and the assumptions you use to account for taxes and the opportunity cost of waiting (investment return you could have made, inflation, etc.). The Social Security Administration has a handy calculator you can use at ssa.gov.

Break-even example.

If you're a top wage earner turning 62 this year and your monthly benefits (in today's dollars) at ages 62 and one month, 66, and 70 are $1,647, $2,233, and $3,019, respectively, then your break-even ages are as follows:

62 (early) vs. 66 (normal retirement age) Break-even age is 77
62 (early) vs. 70 (late) Break-even age is 79 and 6 months
66 (normal retirement age) vs. 70 (late) Break-even age is 81 and 4 months

In this example, if you wait until age 66 vs. age 62 to take Social Security, you'll come out ahead as long as you live past age 76 and 10 months. The break-even age goes up, of course, the longer you wait.