Northern European nations dominate the top 10 in Natixis Global Asset Management’s latest global retirement security ranking.

According to Natixis’ annual Global Retirement Index report, Norway has the most retirement-ready population, followed by Switzerland, Iceland, Sweden, Germany, The Netherlands and Austria. They are joined by New Zealand (No. 4), Australia (No. 6) and Canada (No. 10).

The Natixis Global Retirement Index, introduced in 2013, creates an overall retirement security score based on four factors that affect the lives of retirees.

“Finances in retirement are an important component, but three other sub-indices that gauge material wellbeing, health, and quality of life are included to provide a more holistic view,” the firm explains. “With this year’s edition, Natixis has focused on a smaller number of countries than in the past, mainly developed economies where retirement is a pressing social and economic issue.”

According to Natixis, the U.S. ranking benefits from high per capita income, the stability of its financial institutions and its low rate of inflation. “In addition, the nation’s unemployment rate has moved lower, continuing a long-term trend,” Natixis finds.

But, in contrast to these positive factors, the U.S. also has one of the highest levels of income inequality among developed nations, “putting the goal of retirement savings beyond the reach of millions.”

“The U.S. also has a growing ratio of retirees to employment-age adults, which means there are fewer workers to support programs such as Social Security and Medicare, putting increasing pressure on those government resources over time,” Natixis explains. “That trend, combined with the broader shift from defined benefit to defined contribution employer retirement plans, is transferring the burden of retirement financing to individuals.”

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The Natixis research finds American investors “are acutely aware of increasing the need for individuals to fund a greater share of retirement.”

“However, a large segment of Americans simply don’t have access to employer-sponsored savings programs such as 401(k) plans,” Natixis says, explaining the relatively low ranking for the U.S. despite its immense net material wealth. “The U.S. Department of Labor estimates that one-third of the nation’s workforce doesn’t have access to a retirement plan. A separate Natixis survey of participants in defined-contribution plans found that, even when they have access to a plan, four in 10 contribute less than 5% of their annual salary.”

Natixis further finds U.S. investors see clear hurdles to financial security in retirement, identifying their three greatest challenges as “long-term care and healthcare costs, not saving enough, and outliving their assets.” When asked how they would make up for an income shortfall, two-thirds of U.S. investors unwisely say they will continue to work in retirement.

“Americans must come to grips with their increasing responsibility for their own retirement security,” concludes Ed Farrington, executive vice president of retirement services for Natixis Global Asset Management. “The leading nations in our research are developing effective solutions, but we also need greater commitment by decision makers, engagement by individuals and a willingness to learn from the experiences of other countries around the world.”

The 2016 Natixis Global Retirement Index report is available in full here.