Life expectancy

Life expectancy refers to the average length of time people can expect to live. It is a useful summary indicator of the mortality and health of a nation, an area, or a group of people. Life expectancy data are especially useful for health researchers, and for those involved in the pensions industry.

Babies born in the United States in 2005 are expected to live an average of 77.9 years, according to a 2007 study by the national Centers for Disease Control and Prevention's National Center for Health Statistics. That's an increase of more than 30 years since 1900, when Americans were expected to live just 47.3 years [source:Medline Plus]. While the increase is impressive, America is not at the top of the list for life expectancy. Actually, the United States ranks behind 41 other countries.

Residents of Okinawa, a Japanese island, have long been endowed with high life expectancies. In 2002, there were 34.7 people 100 yearsor older per 100,000 residents, the highest life expectancy of any area in the world [source: USA Today]. People so envy Okinawans' vitality that doctors created a popular diet based on theirs to help others try to live longer. Still, while Okinawa may feature the highest population of centenarians -- people who are 100 years of age or older -- Japan is ranked second in life expectancy with an average of 82.