The Muslim population is increasing at 1.84 percent.
The Muslim population in 2009 was 1.8 billion.
For the latest figures, see World Muslim Population.
The site uses the following sources for their figures:
POPULATION REFERENCE BUREAU
CIA FACT SHEET
THE LIBRARY OF CONGRESS: COUNTRY STUDIES
UNITED STATES DEPARTMENT OF STATE: BACKGROUND NOTES
US DEPARTMENT OF STATE: INTERNATIONAL INFORMATIOON PROGRAM
HOLT, RINEHART & WINSTON: ATLAS
HOPE FOR EUROPE: RESOURCE/LIBRARY SECTION
BBC: RELIGION AND ETHICS