Based on the percentages published in the 2005 CIA World Factbook ("World"), Islam is the second-largest religion in the world. According to the World Network of Religious Futurists, the U.S. Center for World Mission, and the Samuel Huntington, Islam is growing faster numerically than any of the other major world religions. Ontario Consultants on Religious Tolerance estimates that it is growing at about 2.9% annually, as opposed to 2.3% per year global population growth.
This is attributed either to the higher birth rates in many Islamic countries (six out of the top-ten countries in the world
with the highest birth rates have a Muslim majority ) and/or high rates of conversion to Islam.
Commonly cited estimates of the Muslim population today range between 900 million and 1.4 billion
people (cf. Adherents.com); estimates of Islam by country based on U.S. State Department figures yield a total of 1.48 billion, while the Muslim delegation at
the United Nations quoted 1.2 billion as the global Muslim population in Sept 2005.
Only 18% of Muslims live in the Arab world; 20% are found in Sub-Saharan Africa, about 30% in the Indian subcontinental region of Pakistan, India and Bangladesh, and the world's largest single Muslim community (within the bounds of one nation) is in Indonesia. There are also significant Muslim populations in China, Europe, Central Asia, and Russia.
Austria was the first European country to recognize Islam as an official religion, while France has the highest Muslim population of any nation in Western Europe, with up to 6 million Muslims (10%
of the population  ). Albania is said to have the highest proportion of Muslims as part of its population in Europe (70%), although
this figure is only an estimate (see Islam in Albania). The number of Muslims in North America is variously estimated as anywhere from 1.8 to 7 million.