or most of the past year, readers and television viewers heard a great deal - perhaps a great deal too much - about the so-called millennium bug and the havoc it could cause. Consultants were mobilized, funds poured in, and as the clock wound down on 1999 the nation and the world braced themselves, not knowing for sure exactly what would happen.

If only the response had been as swift and as thorough to another looming, and entirely predictable, breakdown: the financial implosion that surely will follow when today's workers retire and government pension programs run out of money.The root of the problem is the ''pay as you go'' system, in which today's workers support today's retirees in hopes that tomorrow's workers - today's children - will do the same for them. That's fine as long as generational cohorts are roughly the same size. But when a statistical anomaly such as the Baby Boom comes along, the formula no longer works.

Governments throughout the developed world have known for many years this problem was developing. But they have taken no effective action to counter the threat.

The United States, for example, has a system in place to set aside a national Social Security ''surplus'' against future demands on the system.

But the surplus is actually being spent on other government programs, in exchange for federal IOUs to be redeemed in the future. If the government cannot meet those future obligations through higher pension withholdings on tomorrow's workers, it will try to get the funds through higher income or other taxes. Either way, a heavy burden will fall on future taxpayers. It's anyone's guess whether they will be willing or even able to pay it.

The problem of too few workers supporting too many retirees will develop at different rates in different countries. In the United States, if current trends continue, the Social Security system is expected to be bankrupt by 2030.

In Britain, taxes will have to double as early as 2020 to meet pension obligations. And in Italy, the number of public-pension recipients already exceeds the number of workers paying into the system.

Legislatures in Europe and North America have tinkered about the edges of the problem. Mainly they have sought to curb future payouts by raising the retirement age or curtailing benefit levels. One fairly drastic variant of that approach, under review in Europe, is to tie benefit payments to national output rather than to earnings.

Perhaps more to the point, governments also are looking into ways to encourage individuals to save privately for their retirements. That's a laudable effort, not least because it is a tacit admission that the public program is inadequate to the task.

The European Union, for example, is developing an EU framework for supplementary private pensions. It would allow more leeway in investing pension assets. It would also let workers carry pension benefits when they switch jobs or move within the EU, and it would reform tax systems to increase private savings.

Congress, too, is considering various ways to encourage workers to take charge of their own pensions. Mostly these involve providing tax incentives for building up private retirement accounts, and ensuring that these funds are managed responsibly.

These efforts would be helped by parallel initiatives to open international markets to providers of private pension-management services. This should be among the aims of the General Agreement on Trade in Services, if it can ignite the new round of global trade talks that fizzled on the launching pad in Seattle last month.

Encouraging private retirement savings plans is, admittedly, a palliative. That's because today's workers still will have to pay considerable sums into a mandatory public system that will never repay them in full.

Ideally, incentives for private retirement savings would be accompanied by commensurate reductions in mandatory contributions to pay-as-you-go government pension schemes.

But short of abolishing Social Security and transferring its income stream to privately managed, individual accounts - a radical solution that could hurt today's retirees and is therefore, regardless of what any candidate says, politically impossible - providing tax and other incentives for private savings is the best most governments can offer.

Today's workers - and even more so, today's children - have a right to at least that level of government response to the demographic time bomb still ticking away into the new millennium.