Think US debt is high? Take a look at Europe's most indebted nations.

In April, the IMF estimated that the US government's debt amounted to 99 percent of gross domestic product. That’s high, but less than four of Europe's five largest debtors.

4. Iceland

Iceland, whose banking system collapsed in 2008, was the first of the Western European countries (although not part of the eurozone) to take a financial hit in the global recession. In January 2009, the Monitor described its 2008 financial meltdown, spurred on by risky banking practices, as the canary in the coal mine for the rest of the region.

Iceland was the world’s fourth-richest nation before its collapse. Three years later, it is still struggling to kick its economic growth back into gear. The sluggish pace is likely going to make it difficult for the country reduce its debt, which in April was at 103 percent of its GDP.

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