The good news: You are likely underestimating how long you’ll live. The bad news: You likely haven’t figured that into your retirement planning.

A recent Brookings Institution study found that most people underestimate their longevity. The study, started 25 years ago, asked 26,000 Americans over the age of 50 what they thought their chances of living to 75 were. Of those who gave themselves a 50 percent chance of reaching 75, about 75 percent reached that milestone. And of those who said they had no chance of reaching 75, about 7 percent of the 26,000, about half survived.

The problem, the Brookings Institution says in its report on financial security in retirement, is that with the move away from company pension and toward individual retirement accounts, there’s a greater responsibility on individuals to plan for retirement.

“Retirees increasingly are self-insuring against a variety of retirement risks, especially the risk of outliving their assets,” it says in the introduction to its report.

And it’s increasingly dangerous to assume that Social Security is going to be able to provide adequate support in retirement.

As of 2010, the money that workers were paying into Social Security no longer covered completely what was being paid to beneficiaries. The program has been using the interest from bonds to pay the difference. By 2020, about five years from now, the Social Security Trust Fund will have to start selling those bonds to pay part of the benefits due retirees. And by 2033, the trust fund will be empty and Social Security will only be able to pay each recipient 77 cents on the dollar.

If the Republicans in Congress wanted to demonstrate what they can do with their newly granted control of Congress, they could begin by weighing options to save Social Security, among them lifting the wage cap so that wages above $113,700 are subject to Social Security taxes; further increasing the retirement age; reforming how cost of living adjustments are calculated; and cutting benefits to future retirees on a sliding scale that protects lower-income recipients. (The Washington Post offers a well-explained look at the problem and possible solutions at tinyurl.com/WaPoSocialSecurity.)

Few are popular options but are less painful than waiting until the cuts have to be immediate and deep.

And while Congress is working on that, each of us owe it to ourselves to plan as if Congress won’t.

If your employer offers a 401(k) program, enroll; open enrollment for such programs starts soon at most companies. If your employer offers a matching contribution, make sure you’re putting in enough of your pay to get the maximum match. And if you don’t have access to a 401(k), enroll in an individual retirement account.

You’re likely going to live longer than you thought; now you have to make sure you can afford it.