Muslims are the fastest-growing religious group in the world. The growth and regional migration of Muslims, combined with the ongoing impact of the Islamic State (also known as ISIS or ISIL) and other extremist groups that commit acts of violence in the name of Islam, have brought Muslims and the Islamic faith to the forefront of the political debate in many countries. Yet many facts about Muslims are not well known in some of these places, and most Americans – who live in a country with a relatively small Muslim population – say they know little or nothing about Islam.

Here are answers to some key questions about Muslims, compiled from several Pew Research Center reports published in recent years:

How many Muslims are there? Where do they live?

There were 1.6 billion Muslims in the world as of 2010 – roughly 23% of the global population – according to a Pew Research Center estimate. But while Islam is currently the world’s second-largest religion (after Christianity), it is the fastest-growing major religion. Indeed, if current demographic trends continue, the number of Muslims is expected to exceed the number of Christians by the end of this century.

Although many countries in the Middle East-North Africa region, where the religion originated in the seventh century, are heavily Muslim, the region is home to only about 20% of the world’s Muslims. A majority of the Muslims globally (62%) live in the Asia-Pacific region, including large populations in Indonesia, India, Pakistan, Bangladesh, Iran and Turkey.

Indonesia is currently the country with the world’s largest Muslim population, but Pew Research Center projects that India will have that distinction by the year 2050 (while remaining a majority-Hindu country), with more than 300 million Muslims.

The Muslim population in Europe also is growing; we project 10% of all Europeans will be Muslims by 2050.

How many Muslims are there in the United States?

In 2015, according to our best estimate, there were 3.3 million Muslims of all ages in the U.S., or about 1% of the U.S. population. Pew Research Center’s 2014 Religious Landscape Study (conducted in English and Spanish) found that 0.9% of U.S. adults identify as Muslims. A 2011 survey of Muslim Americans, which was conducted in English as well as Arabic, Farsi and Urdu, estimated that there were 1.8 million Muslim adults (and 2.75 million Muslims of all ages) in the country. That survey also found that a majority of U.S. Muslims (63%) are immigrants.

Our demographic projections estimate that Muslims will make up 2.1% of the U.S. population by the year 2050, surpassing people who identify as Jewish on the basis of religion as the second-largest faith group in the country (not including people who say they have no religion).

A recent Pew Research Center report estimated that the Muslim share of immigrants granted permanent residency status (green cards) increased from about 5% in 1992 to roughly 10% in 2012, representing about 100,000 immigrants in that year.