AT 75, Social Security is starting to show its age. The major source of retirement income for millions of Americans, Social Security has a significant deficit in cash flow.

Worse, its long-term picture is bleak. Social Security owes $7.7 trillion more in benefits than it will take in from payroll taxes, over the next 75 years. The payroll taxes won’t keep up with expenditures beginning in about six years.

Social Security can cover all promised benefits for years, but doing nothing is not an option. If changes aren’t made fairly soon, retirees eventually will face 22 percent benefit cuts.

No silver bullet can painlessly enable the program to keep paying the same level of benefits it has. Fixing Social Security will require a combination of several reforms — some more difficult than others.

One needed reform is to increase the Social Security retirement age. This should be accompanied by incentives, such as eliminating the Social Security payroll tax for employees who are willing to work beyond normal retirement age.

Increasing Social Security eligibility ages would simply reflect longevity improvements that have taken place. Future retirees will live longer, on average, than their grandparents did. Social Security must reflect that increased longevity by increasing retirement ages for both full benefits and early retirement benefits. Otherwise, recipients will spend an ever higher proportion of their lives living at the expense of their children and grandchildren.

Life expectancy has increased substantially since 1950. Boys born in 2004 can expect to live almost 10 years longer than those born in 1950; women can expect to live nine years longer.

When the Social Security program was created in 1935, 65-year-old men could expect to spend about 13 years in retirement — 16 percent of their lifetime. Women of the same age averaged 15 years — or 18 percent of lifespan — in retirement. However, only a little more than half of adults older than 21 lived to reach retirement age.

Today, a male retiree born in 1940 will spend 19 percent to 25 percent of his life collecting Social Security benefits — depending on whether he retired at age 65 or chose early retirement. A woman born in the same year will collect benefits for 21 percent to 27 percent of her life.

Social Security has not kept pace with these changes. Congress has not changed the age for receiving full benefits since 1983, when it approve a phased increase leading to retirement at age 67 in 2022. The early eligibility age is unchanged since 1961.

Eligibility should be increased to age 68 by 2023 for full benefits and to age 65 for early retirement, but it’s not a step I recommend lightly.

Many who wish to work longer may have health issues or disabilities that make it impossible to delay retirement. Workers with physically demanding jobs are most likely to face these issues. They should not be penalized by higher age requirements. Instead, they should receive benefits through Social Security’s disability insurance program until they reach the new retirement ages.

Social Security is and should remain a key part of Americans’ retirement security system. Congress must have the courage to let some of today’s workers know they will need to work longer before they can receive Social Security benefits.

This may not be a pleasant message, but it is fair. Further delay will force Congress to make an even more unpalatable decision as Social Security’s finances worsen.

David John is a senior research fellow in retirement security at The Heritage Foundation.