For information about how data for each country or territory were collected and analyzed, see Data Sources by Region. Sources include national censuses, demographic and health surveys, and other general population surveys and studies. Population figures for previous years have been projected forward to 2009 based on the assumption that the Muslim population of the country is growing at the same rate as the general population. (See Methodology for Muslim Population Estimates.)
Data for countries marked with an asterisk (*) are drawn primarily from general population surveys, which have smaller sample sizes than demographic surveys and are not designed to measure the size of small minority populations. This may lead to undercounts of Muslims in countries where they represent a small minority of the population and overcounts where they represent the vast majority of the population. Those numbers, therefore, should be considered more approximate.