Figuring out when to take Social Security is a tough decision. You can generally claim retirement benefits at any age between 62 and 70, and the longer you wait, the larger your monthly check will be. A host of factors go into making a smart decision about Social Security, and there are good reasons why one decision might be better than another in your particular situation.

You can find plenty of articles where I've talked about smart reasons to take Social Security at 62. Yet with statistics showing that more people claim Social Security at 62 than at any other age, I'm convinced that a large number of smart people are actually making a mistake when they take their benefits as early as possible. Here are some reasons why even smart people can make what turns out not to have been the best decision for their personal views of what they want retirement to be.

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1. Miscalculating life expectancy

One common mistake people make about Social Security is assuming that they won't live long enough to make waiting worthwhile. It's true that in order to justify not claiming at your first opportunity, you have to be confident that the higher monthly payments you'll get from waiting will more than make up for the lost checks that early claimers get. Even with life expectancies at birth having grown from around 70 half a century ago to nearly 79 today, those figures are just enough for late-filers to break even compared to those who file early.

The problem is that when you're 62 and considering a smart Social Security decision, you can't use life expectancies at birth. Instead, you need to take the higher life expectancy for someone who has already survived to age 62. Currently, that figure is more than 20 years, meaning that the typical 62-year-old will live to be 82. That's enough to push the analysis in the other direction, making a later claim more valuable in the long run.

2. Overlooking a spouse's needs

If you're single, then claiming Social Security is all about how it affects your finances. But if you're married and the primary earner for the family, then it's easy not to realize that the decisions you make with your Social Security also affect your spouse.

Your spouse is entitled to survivor benefits after you pass away, and that benefit is based in part on when you decide to take your retirement benefit. Essentially, claiming early not only reduces your payment but also penalizes your spouse for your impatience, reducing the survivor payment as well. Even if it would be smart for you to claim early based on just your own health and other financial reasons, it might well be in your family's overall best interest for you to wait and thereby boost the amount your spouse receives after you pass away.