Census Bureau's Question and Answer Series:
Does the U.S. Census Bureau produce population data for other countries and the world?
"The International Data Base (IDB) provides country rankings and other world population information sources. Using Data Access from the IDB allows you to create demographic indicators, tables, pyramids, and data source information by Country, Region, and Age Groups for years 1950 to 2050. For assistance using the IDB, you can contact the Demographic Call Center at 301-763-2422 or toll-free at 1-866-758-1060."