UNDER SIEGE

Germany established the world's first widely available state pension system in 1889. The United States introduced Social Security in 1935. In the prosperous years after World War II, governments expanded pensions. Companies began to offer pensions that paid employees a guaranteed amount each month in retirement - so-called defined-benefit pensions.

The average age at which men could retire with full government pension benefits fell from 64.3 years in 1949 to 62.4 years in 1999 in the relatively wealthy countries that belong to the Organization for Economic Cooperation and Development.

As the 2000s dawned, governments - and companies - looked at actuarial tables and birth rates and realized they couldn't afford the pensions they'd promised.

The average man in 30 countries the OECD surveyed will live 19 years after retirement. That's up from 13 years in 1958.

The OECD says the average retirement age would have to reach 66 or 67, from 63 now, to "maintain control of the cost of pensions" from longer lifespans.

Compounding the problem is that birth rates are falling just as the bulge of people born in developed countries after World War II retires.

Populations are aging rapidly as a result. The higher the percentage of older people, the harder it is for a country to finance its pension system because relatively fewer younger workers are paying taxes.

In response, governments are raising retirement ages and slashing benefits. In 30 high- and middle-income OECD countries, the average age at which men can collect full retirement benefits will rise to 64.6 in 2050, from 62.9 in 2010; for women, it will rise from 61.8 to 64.4.

In the wealthy countries it studied, the OECD found that the pension reforms of the 2000s will cut retirement benefits by an average 20 percent.

The fate of government pensions is important because they are the cornerstone of retirement income. Across the 34-country OECD, governments provide 59 percent of retiree income, on average.