Your Social Security benefits are calculated based on how much you earned during your top 35 working years, but the age at which you first file for those benefits can impact the amount of money you receive each month. If you wait until your full retirement age (FRA) to take benefits, you'll get the full monthly amount you're entitled to based on your earnings record. FRA is a function of your year of birth, and for today's workers, it's either 66, 67, or 66 plus a certain number of months.

That said, you actually get an eight-year window to file for Social Security that begins at age 62 and ends at age 70. If you file ahead of FRA, you'll reduce your benefits depending on how early you jump the gun. On the other hand, if you hold off on taking benefits past FRA, you'll accrue delayed retirement credits that boost your payments by 8% a year. Because this incentive runs out at age 70, that's generally considered to be the latest age to file for Social Security -- even though you're technically not required to do so.

Older man sitting in a boat

IMAGE SOURCE: GETTY IMAGES.

Still, there's a lot to be gained by taking benefits as late as possible and growing them to the maximum extent. So why is it that only 3% of men and 5% of women wait to claim Social Security at 70, while all other beneficiaries file before that point? Here are a few explanations.

1. They need the money sooner

One major reason why so many seniors take Social Security before age 70 or before FRA, for that matter, is that they're forced to retire sooner than they want to. In fact, data from Voya Financial tells us that 60% of workers leave their jobs ahead of schedule and the reasons run the gamut from health issues to layoffs. Compounding this issue is the fact that most workers aren't saving well for retirement, so that when they end up retiring sooner than planned, they don't have the money to support themselves, and therefore must turn to those benefits rather than wait.

2. They want the money sooner

Not everyone is forced into early retirement, though. While most Americans are behind on building their nest eggs, there also are those who are saving quite nicely. For workers in the latter camp, filing for Social Security before age 70 means getting access to that money at a time when they're young enough to really enjoy it.

Of course, not growing your benefits as much as possible can be detrimental if your savings are poor. But if you're sitting on a healthy nest egg and your plan is to have your Social Security income serve as fun money and nothing more, it often makes sense not to wait.

3. They're afraid Social Security is going broke

One final reason why most seniors aren't waiting on Social Security is that they're buying into the rumors that the program is going broke. And make no mistake about it -- those really are just rumors. While the program is facing financial difficulties, it's virtually impossible for Social Security to go broke because its funding comes from payroll taxes. Therefore, as long as we have a workforce, the program will keep getting money to pay beneficiaries.

That said, the program soon will start paying out more than it takes in, and while it has a trust fund it can tap into to make up the difference, that fund will only last for about another 16 years. Once that fund runs out, Social Security may have to slash benefits if Congress doesn't step in and fix its impending shortfall.

But we have a long way to go until that happens -- if it happens -- so at present, this shouldn't be a major point of concern. Still, it's enough to drive many seniors to take their benefits earlier rather than later.

Should you file for Social Security at 70?

Now that you understand why most people don't claim benefits at 70, the question is: Should you wait the maximum amount of time? Or should you file at FRA, or even as soon as you're eligible?

The answer is that it really depends on your personal circumstances. If you don't have a lot of savings, then it pays to grow your benefits as much as possible to ensure that you're able to cover the bills as a senior. Even if you don't need the money, if you're still working come FRA and aren't in a rush to have your cash, you might as well hold off on Social Security, boost your benefits, and enjoy the extra money later on.

There's no hard and fast rule stating that you must claim Social Security at 70. Just make sure to consider the advantages of doing so before filing sooner.

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