Through 2050,the United Statesis projected to remain in third place behindIndiaandChinaamong the world's most populous countries, according to the U.S. Census Bureau. These findings are derived from the population estimates and projections for 228 countries and areas released today through the Census Bureau'sInternational Data Base. This release includes revisions for 19 countries and provides information on population size and growth, mortality, fertility and net migration.

"The Census Bureau has been preparing individual country population estimates and projections for more than 50 years," saidLoraine West, a demographer in the Census Bureau's Population Division. "Current estimates and projections are provided through 2050 and are routinely updated as new data become available."

Althoughthe United Stateswill maintain its third place position, the ranking of the countries with the 10 largest populations in the worldis expected to change over the next few decades.

The top 10 countries each currently have at least 125 million inhabitants.RussiaandJapanare projected to soon fall out of this group because of persistent low fertility rates, which have already caused their populations to decline.Russia's decline is also due in part to relatively high mortality.

The countries expected to advance in the rankings are those with high fertility.Ethiopia, in particular, with an estimated fertility rate of 6.0 children per woman in 2011, is projected to vault from 13th to seventh on the list of most populous countries by 2050, tripling in total population from 91 million to 278 million.Nigeriaalso has a relatively high estimated fertility rate of 5.7 and is projected to more than double its population by 2050 from 166 million to 402 million.

Currently seventh on the list of most populous countries, by 2050,Nigeriais projected to climb to fourth.

Other developing countries, such asBangladesh,BrazilandIndonesia, while continuing to grow, will drop slightly in the rankings given that their fertility already is lower thanEthiopiaandNigeria.

ChinaandIndia, the only countries with more than a billion people, are expected to continue to occupy the top two positions, although their order is projected to switch by 2025 whenIndiais expected to overtakeChinaas the world's most populous country.

By 2050,the Philippineswill round out the world's most populous countries, reaching 10th on the list with a projected population of 172 million.

The 19 countries included in this update areAfghanistan,Angola,Azerbaijan,Comoros,Curacao,French Polynesia,Japan,Kazakhstan,Kenya,Liechtenstein,Moldova,Netherlands,Nigeria,Qatar,Singapore,Sint Maarten, Suriname,United Statesand theBritish Virgin Islands.

The Census Bureau's International Data Base includes projections by sex and age for countries and other areas with populations of 5,000 or more. Population projections incorporate assumptions about future trends in fertility, mortality and migration. In general, fertility and mortality are projected based on recent trends and migration for each country typically reflects recent trends but also considers longer-term levels of migration. The level of uncertainty is greater for projections further in the future.