A new, comprehensive study of over 200 countries finds that there are 1.57 billion Muslims of all ages living in the world today - 23% of an estimated 2009 world population of 6.8 billion.

The biggest gains due to change in religious affiliation in the US have been among those who say they are not affiliated with any particular faith, according to a new study.

A new study from the influential Pew Forum on Religion & Public Life charts the major demographic changes in US religious life, especially the impact of the growing Spanish-speaking population.