Our Social Security problem is just one aspect of a larger retirement revolution – an upheaval in medicine, life expectancy, and work. Since Social Security’s creation in 1935, life spans have increased dramatically. Someone who now reaches 65 can expect to live almost another 20 years.

Meanwhile, government has constantly made Social Security and Medicare more generous. The result is “middle-aged retirement,” as Eugene Steuerle of the Urban Institute calls it. If people retired for the same number of years now as in Social Security’s early years, he says, they’d work until 74. In fact, half of Social Security recipients start benefits at age 62.

We can no longer afford this system: Its costs will overburden future generations and could weaken the economy. As Congress considers Social Security legislation, it ought to design a broad makeover of retirement.

Americans should work longer. We’re healthier and – as the number of new workers shrinks – society will need older workers. Social Security and Medicare were originally intended to protect the neediest among the elderly; they should not subsidize ever-longer retirements.

Unfortunately, the odds of this sort of makeover are slim. The Social Security debate has predictably degenerated into a bitterly partisan exercise in public confusion that obscures some basic realities. As I’ve noted in earlier columns, these are daunting.

Let’s review them. By 2030, spending on Social Security, Medicare, and Medicaid (which provides nursing home care) is projected almost to double as a share of national income (gross domestic product). To hold federal spending constant – again as a share of GDP – would mean eliminating almost 50% of the remaining spending on non-retirement programs. If we paid for higher retirement spending with taxes, we’d have to raise taxes at least 30%.

To me, neither outcome is desirable. If you agree, then the only alternative is to cut retirement benefits. Baby boomers can’t be excluded, because they’re the people getting older. We need to prod them to work longer – and to mix work and retirement – by reducing the subsidies that encourage earlier retirement. For those who truly can’t work longer, there’s a disability program. Let me sketch what’s needed.

My aim is to trim the increases in federal retirement spending by half in 2030. Because the projected increases are between 6% and 7% of GDP, the required savings is about 3.5% of GDP. Here’s what I suggest:

– Raise Social Security’s normal retirement age to 70. Under present law, it reaches 67 in 2027.That’s too slow. Increasing it to 70 by 2030 would require increases of about two months a year. The savings in 2030: about 0.8% of GDP.

– Cut Social Security benefits by 20. Spare retirees whose wages were average or less than average. Above that, cuts would be steeper as retirees got wealthier. Reductions would (again) be phased in slowly. The 2030 savings: about 0.9% of GDP.

– Raise Medicare’s eligibility age slowly to age 70 by 2030. People from 65 to 70 could get the choice of buying Medicare protection. The 2030 savings: about 1% of GDP.

– Require Medicare recipients to pay 20% of the program’s costs through premiums. Beneficiaries now pay about 12%. Premium increases should be introduced gradually, and wealthier retirees should pay more. The 2030 savings: 0.5% of GDP.

– Tax Social Security as ordinary income. A lot is now exempt from the income tax. The 2030 savings: 0.2% of GDP.

My estimates are admittedly crude, possibly wrong. Without official projections of my proposals, I’ve made educated guesses using many sources. Assuming the figures are roughly correct, future retirement spending – and taxes – will still increase because there will be more retirees living longer and using more medical services.

These proposals will be seen as harsh. They aren’t. People who reach 62 or 65 or 70 have no automatic claim on their juniors. Why is it that a couple in their 30s with two children, car payments, and a mortgage should subsidize the retirement of a couple in their mid-60s with no mortgage, whose children are long gone, and who could still work?

The only answer is that older couples expect to be subsidized (in part because they’ve spent their lives subsidizing their elders) and will be furious if they aren’t.

But that is politics, not a moral or social justification. If Americans have to work longer, the economy will create the needed jobs. The real obstacle is the expectation that people in their early 60s are entitled to stop working.

Doubtlessly, many Americans prefer having someone else support their leisure. But that was not the original purpose of Social Security or Medicare. We need to move these programs back toward their origins.