What is your Social Security account really worth? The answer: a lot more than you think.

Many a worker imagines that he or she would be better off without compulsory Social Security taxes. But it takes a lot of money to guarantee yourself a monthly income for the rest of your life -- especially one that rises with the inflation rate.

I asked Social Security to compute what a 1990 retiree would need, in a single lump sum, to duplicate the lifetime, inflation-indexed annuity that Social Security provides. I assumed inflation at 4 percent and asked about a woman aged 65.

Had she earned the maximum Social Security wages all of her life, she'd retire on a monthly income of $975 this year, according to Social Security's Harry Ballantyne. To pay herself the same monthly income, plus an extra 4 percent a year over her life expectancy, she'd need a kitty worth $177,000, earning 6 percent interest after taxes.

That's a lot of money to save, even with your employer's help. And all it supplies is a basic income. You'd need a far larger pot of investments in order to supplement your $975.

Had this retiree earned what Social Security calls an "average" paycheck all of her life, and quit in 1990 at age 65, she'd be getting $720 a month. To supply that, indexed at 4 percent, she'd need a nest egg of $131,000, also invested at 6 percent after taxes.

Insurance professionals will object that, with $177,000, a 65-year-old woman can find a much larger lifetime annuity in the private market. Social Security, they say, is being cheap.

On the other hand, her payroll taxes also financed a lifetime of Social Security disability insurance and life insurance. Had she died, her dependents would have gotten a government income. So your Social Security annuity cannot be compared directly with a private-insurance annuity.

But even if they could be compared, all this is fantasy. Americans have trouble saving three months' income for an emergency fund. They'd never save an extra $177,000 to replace a government retirement fund, voluntarily abandoned.

If they tried, they would almost certainly raid their fund from time to time for consumer purchases. This is exactly what happens to employee retirement funds. The majority of workers who leave their jobs and get a lump-sum payout don't save it.

In short, for retirement savings, Social Security is hard to beat. Its compulsory nature is what makes it work. If the system were voluntary, many more of our elderly would die poor.

If you're a younger worker, you may not be so much offended by the compulsory nature of the tax as by the fear that you'll never collect. When the time comes for you to retire, you worry, the Social Security tank will be dry.

It'll never happen. If you doubt me, just look around and count the votes. How many among us would vote to abolish Social Security? What is the future of any politician who would propose it?

It is true, however, that Social Security benefits won't be worth quite as much in the future. Your checks will replace a smaller percentage of your working income than they do today.

What's more, the retirement age is moving up. Today, full benefits are paid at age 65. But beginning in the year 2000, the age for getting full benefits will gradually increase to age 67.

So even though you'll receive Social Security, and it will be worth a substantial sum, you still should be saving more on your own today.