The report offers the most up-to-date and fully sourced estimates of the size and distribution of the worldwide Muslim population, including sectarian identity. Previously published estimates of the size of the global Muslim population have ranged widely, from 1 billion to 1.8 billion. But these commonly quoted estimates often have appeared without citations to specific sources or explanations of how the figures were generated. The Pew Forum report is based on the best available data for 232 countries and territories. Pew Forum researchers, in consultation with nearly 50 demographers and social scientists at universities and research centers around the world, acquired and analyzed about 1,500 sources, including census reports, demographic studies and general population surveys, to arrive at these figures – the largest project of its kind to date. These findings on the world Muslim population lay the foundation for a forthcoming study by the Pew Forum, scheduled to be released in 2010, that will estimate growth rates among Muslim populations worldwide and project Muslim populations into the future. The Pew Forum plans to launch a similar study of global Christianity in 2010 as well. The Pew Forum also plans to conduct in-depth public opinion surveys on the intersection of religion and public life around the world, starting with a 19-country survey of sub-Saharan Africa scheduled to be released later this year. These forthcoming studies are part of a larger effort - the Global Religious Futures Project, jointly funded by The Pew Charitable Trusts and the John Templeton Foundation - that aims to increase people’s understanding of religion around the world.