Updated

Iceland is the world's best place to live, according to an annual U.N. report that ranked sub-Saharan Africa as the worst place for someone to call home.

The island nation edged out Norway, which had held the top spot for the last six years. The United States slipped to 12th place from an eighth place ranking last year.

The U.N. Human Development Index used 2005 figures for life expectancy, educational levels and real per capita income to rank 175 nations of the world — plus Hong Kong and the Palestinian territories — for habitability. Rich, free-market economies dominated the top spots with Australia, Canada and Ireland rounding out the top five.

Click here to view the report.

African countries landed at the bottom of the list, where in 10 countries, two in five children will not reach the age of 40. All 22 of the lowest ranked countries are in sub-Saharan Africa, with Sierra Leone placing last. Last year's report cited HIV/AIDS' "catastrophic effect" on the region's life expectancy.

The disconnect between the top-ranked nation and the lowest for per capita GDP is staggering. Iceland boasts a GDP 45 times higher than in Sierra Leone.

The index, published annually since 1990, does not include 17 countries, including Iraq, Afghanistan and Somalia, due to insufficient data.

Norway slipped to No. 2 this year because of new life expectancy estimates and updated figures for gross domestic product, or GDP, the report said.

U.N. officials downplayed shifts in rankings among the top contenders, including the U.S., saying that if data had been available, the United States would have been in 10th, not eighth place.

The United States gets good marks for real per capita GDP, which at $41,890 is second only to that of Luxembourg ($60,228), but fares less well on life expectancy — tied last in the top 26 countries, along with Denmark and South Korea, at 77.9 years.

Japan has the longest life expectancy at 82.3 years, and Zambians, the lowest, at 40.5.

The human development index has risen over the last 30 years for most nations, but in 16 it was lower than in 1990, and in three — the Democratic Republic of Congo, Zambia and Zimbabwe — lower than in 1975.