The United States currently has the greatest number of centenarians in the world, estimated at 96,548 on November 1, 2008. ^[1] The U.S. number is partly a function of America's large population in 1890-1910, large farm population a century ago, and an increased emphasis on long-term care facilities.

Japan is second, with 36,276 in September 2008.^[2] Many experts attribute this (and Japan's very high life expectancy) to the Japanese diet, which is particularly low in fats and to hygienic practices. In addition, five times the rate of Okinawans live to be 100 than the rest of Japan.^[3] In addition to diet, there are four other factors that have been found to increase the life expectancy for Okinawans, as noted later in the "research into centenarians" section of this article. ^[4]

France has the highest rate of centenarians in percentage of the total population: 20,115 centenarians in metropolitan France for a little less than 62 millions inhabitants, or 1 centenarian for 3,076 people. The rate is 1 per 3,522 in Japan^[5] (but much higher in Okinawa), and 1 per 3,300 in the United States.^[6]"

The U.S. Census Bureau has forecast that the number of Americans aged 100 or older will increase by more than 22 times the 1990 estimate of 37,306. In October 2001, the US Census Bureau actually reported that there were 50,454 US centenarians (a more reasonable 35 percent increase) out of a total population of 281.4 million Americans.

From present data, the numbIer of worldwide centenarians is around 450,000. However, if one considers only the total number of supercentenarians, this number falls dramatically to an estimated 300 to 450 worldwide, of which only approximately 80 are validated.

The book "Healthy at 100" by John Robbins is a facinating study of people at are over 100.    I am not giving away any trade secrets as it is right on his web site, the number one correlation of a factor and long life is family  and friends.   There are places that seem to have a concentration of Centenarians call Blue Zones.  Blue Zones is a term coined by Dan Buettner.   In his travels on bike treks all over the world he became interested in location that had a high number of people over 100 years of age.  They are very specific: 

http://en.wikipedia.org/wiki/Blue_Zone

Five Blue Zones have been discovered:

• Sardinia, Italy: One team of demographers found a hot spot of longevity in mountain villages where men reach the age of 100 years at an amazing rate.
• The islands of Okinawa, Japan: Another team examined a group that is among the longest lived on Earth.
• Loma Linda, California: Researchers, studied a group of Seventh-day Adventists who rank among America's longevity all-stars. Residents of these three places produce a high rate of centenarians, suffer a fraction of the diseases that commonly kill people in other parts of the developed world, and enjoy more healthy years of life. ^[1]
• Nicoya Peninsula, Costa Rica: The Nicoya Peninsula was the subject of research on a Quest Network expedition which began on January 29th, 2007.^[2]
• Icaria, Greece: The April '09 expedition to the island of Ikaria uncovered the location with the highest percentage of 90 year-olds in the planet - nearly 1 out of 3 people make it to their 90s. Furthermore, Ikarians "have about 20 percent lower rates of cancer, 50 percent lower rates of heart disease and almost no dementia.

The following is a diagram that shows common traits: