Retirement systems vary widely from country to country. In China, policymakers are just beginning to expand retirement benefits to everyone. In Australia, people have been compelled for years to save for their own retirements. Italy and Germany are raising retirement ages and cutting benefits.

Here's a look at retirement systems in key nations:

— UNITED STATES:

The United States is struggling to finance its promises to future retirees. Social Security is the core of its system. Social Security payments are financed by a tax on both workers and employers. The payments average $1,269 a month. Two-thirds of retirees rely on Social Security for most of their income. Americans can collect as early as age 62 but don't receive the full benefit unless they wait later to collect — until age 66 for those born from 1943 through 1959 and age 67 for those born after. Many also rely on corporate pensions. But companies have been replacing them with 401(k)-style plans. These plans require employees to save and invest themselves. But many who are eligible for 401(k) or similar plans don't enroll in them, contribute too little or raid their accounts before retirement.

— CHINA:

China's population is aging rapidly. That has left a shortage of working-age people to pay into the pension system. For now, the retirement system remains generous for most city dwellers. Urban workers pay 8 percent of their income toward retirement; their employers add 20 percent. The pensions equal about half of pre-retirement income. Men are eligible for pensions at 60, women at 50 to 55. Only about half of adults are covered by the urban pensions or similar pensions that are available to government workers. In 2009, China introduced a pension plan for rural areas. But it's barely begun. And it pays rural retirees an average of just $12 a month. Policymakers are considering raising the retirement age for urban workers. China tightly regulates investing, making it difficult for workers to put money in riskier investments that offer higher returns and the potential to build significant retirement savings. China is reviewing ways to ease investment restrictions.

— JAPAN:

An aging Japan is struggling to finance the retirement of its baby boom generation. It has a three-part system: Workers receive a flat-rate pension of about 66,000 yen ($657) a month from a fund partially financed by worker contributions. They also receive a second pension based on their earnings, financed entirely by their contributions. And they can contribute to additional plans that are voluntary. They can collect the flat-rate pension after contributing for 25 years; they become eligible for a full benefit after 40 years. The flat-rate and earnings-based pensions combined replace an average of only about 25 percent of pre-retirement income. Many older Japanese, who had lifetime jobs with good benefits, have accumulated hefty savings. But younger workers, who came of age amid a sluggish economy and corporate cutbacks, are struggling to save.

— GERMANY:

Germany's retirement system is generous for many, but getting less so. The post-World War II economic boom financed comfortable retirements. The system still provides the bulk of income for retired people — about 70 percent as of 2010. Germans can retire with a full pension at 65, though the age is gradually rising. People born after 1964 face a retirement age of 67. The system replaces 58 percent of average take-home pay. The pensions are funded by a payroll tax with no investment assets backing the government's promises — a so-called pay-as-you-go system. Pensions are tied to earnings during a person's working years. But the formula now reduces pension levels as the ratio of retirees to workers rises. There's an additional benefit that serves as a safety net for very low-income retirees. Many people who work for major employers also have company-based pensions.

— FRANCE:

Older French workers who want to retire early have a good deal: The minimum age for a full pension for most of them is just 62 as long as they've contributed to the system for at least 41.5 years. France has a tax-funded pension and mandatory employer programs. A worker who earned France's median wage receives 60.8 percent of pre-retirement take-home pay. In October, France raised the contribution period to receive a full public pension from 41.5 to 43 years — but only after 2020. By then, most of France's baby boomers will have retired.

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