If you want to retire comfortably in the United States, you need to either strike it rich or invest a lot of money in a 401(k) or other private retirement plan. If you rely solely on Social Security for retirement income, you’ll have a hard time just paying the bills. That’s not the case in certain other countries that offer generous pension systems to all residents.

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According to the Mercer CFA Institute Global Pension Index, which benchmarks 47 retirement income systems around the world, the Netherlands has the best overall pension system in the world. The United States landed around the middle of the pack, ranking No. 22 out of 47 and getting an overall grade of C+. Much of that grade was based on the Social Security system, though Mercer also looked at private pension and retirement plans.

In its report, published last year, Mercer scored countries based on three main categories: adequacy, sustainability and integrity. Adequacy measures the amount of money pensioners receive and how well it helps them financially. Sustainability looks at whether the system can keep delivering, while integrity gauges a system’s trustworthiness.

The average overall index score across all countries analyzed was 63.0 — which is exactly what the United States got. The U.S. scored above average in adequacy (66.7 vs. the average of 64.8) and sustainability (61.1 vs. the average of 54.2). It did poorly in integrity, with a score of 59.5 vs. the average of 72.2, which put the U.S. among the lowest in that category.

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According to Mercer, the overall index value for the U.S. system could be increased by doing the following:

• Raising the minimum benefit for low-income individuals

• Improving the vesting of benefits and protecting the real value of benefits until retirement

• Limiting access to benefits before retirement

• Requiring that part of retirement benefits be taken as an income stream

While the U.S. languished in the middle of the pack, a trio of European countries landed at the top of Mercer’s ranking. Here are the countries with the best retirement systems in the world.

1.The Netherlands

• Overall score: 85.0

• Adequacy: 85.6

• Sustainability: 82.4

• Integrity: 87.7

2. Iceland

• Overall score: 84.8

• Adequacy: 85.5

• Sustainability: 83.8

• Integrity: 85.0

3. Denmark

• Overall score: 81.3

• Adequacy: 82.5

• Sustainability: 82.5

• Integrity: 77.8

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4. Israel

• Overall score: 80.8

• Adequacy: 77.0

• Sustainability: 82.7

• Integrity: 84.4

5. Australia

• Overall score: 77.3

• Adequacy: 70.7

• Sustainability: 78.4

• Integrity: 86.1

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This article originally appeared on GOBankingRates.com: These 5 Countries Have the Best Retirement Plans in the World