You recently gave an example of a Social Security benefit that would be $2,000 if taken at age 66, or $2,640 if taken at age 70. But if you delay until 70 to collect, you’re forgoing 48 months of $2,000 checks, or $96,000. You’d have to live to age 82.5 to “break even” — i.e., make up that $96,000. ($96,000 divided by $640 = 150 months.) Wouldn’t it make sense to take the $2,000 and invest it, rather than wait four years without payments?

Only if you could put those monthly $2,000 checks into an investment that’s risk-free, inflation-adjusted and pays more than 8 percent a year. That investment doesn’t exist.

Actuaries say the “break-even“ calculation is more complex than you think because it depends on inflation rate and tax rate assumptions. But you’re right that delay involves a trade-off most Americans can’t afford.

Whether postponing Social Security makes sense depends on your financial situation, your health and your marital status. (When you delay your application, your surviving spouse inherits your enhanced benefit even if you die before collecting.)

The compelling argument for waiting isn’t the somewhat bigger starting benefit. It’s that delay means a substantially larger benefit when you and/or your spouse are in your 80s and 90s. And yes, chances are you’ll live that long. The Society of Actuaries says on average, a 65-year-old man now lives to age 86.6, and a 65-year-old woman to age 88.8 — and if they’re married, there’s a 70 percent chance at least one of them will live to be 90, and a 44 percent chance at least one of them will live to be 95.

THE BOTTOM LINE Delaying Social Security past age 66 makes sense if you’re healthy and have enough savings to live on, or will continue working while you wait.