Three years ago the Pew Research Center’s Forum on Religion & Public Life launched an effort to generate up-to-date and fully sourced estimates of the current size and projected growth of the world’s major religious groups. As part of this multi-phase project, the Pew Forum has assembled data on the size and geographic distribution of eight major religious groups – including the religiously unaffiliated – as of 2010. These estimates are presented in this report.

The estimates are based on a country-by-country analysis of data from more than 2,500 censuses, surveys and official population registers that were collected, evaluated and standardized by the staff of the Pew Forum over the past several years. Researchers at the International Institute for Applied Systems Analysis (IIASA) in Laxenburg, Austria, and at the Vienna Institute of Demography in Vienna, Austria, collaborated on the analysis.

This effort is part of the Pew-Templeton Global Religious Futures project, which analyzes religious change and its impact on societies around the world. The project is jointly and generously funded by The Pew Charitable Trusts and the John Templeton Foundation.

In order to present data that are comparable across countries, this study focuses on groups and individuals who identify themselves in censuses, large-scale surveys and other sources as being members of five widely recognized world religions – Buddhism, Christianity, Hinduism, Islam and Judaism. The study also includes estimates for the size and geographic distribution of three other groups: the religiously unaffiliated (those who say they are atheists and agnostics, as well as people who do not identify with any particular religion in surveys); adherents of folk or traditional religions, including members of African traditional religions, Chinese folk religions, Native American religions and Australian aboriginal religions; and adherents of other religions.

Some of the faiths that have been consolidated into the “other religions” category, such as the Baha’i faith, Jainism, Sikhism, Shintoism and Taoism, have millions of adherents around the world. However, in the overwhelming majority of countries, these religions are not specifically measured in censuses and large-scale surveys. For example, among the census and survey data we found from recent decades, Sikhs are measured in fewer than 20 countries.

In addition to providing estimates on the size and distribution of the world’s major religions, this report also includes information on the religious groups’ median ages, both globally and in particular regions. The age composition of a religious group is one of several factors that influence population growth, along with such factors as fertility and mortality rates, religious switching and migration. These factors will be explored in future Pew Forum reports.

The new study on the global religious landscape as of 2010 complements two previous reports by the Pew Forum on the size and distribution of the world’s Christian and Muslim populations: “Mapping the Global Muslim Population” (October 2009) and “Global Christianity” (December 2011). A third report, “The Future of the Global Muslim Population” (January 2011), projects the future growth of the world’s Muslim population through the year 2030. The Pew Forum is now collaborating with IIASA researchers to project the future growth of all major religious groups, including the religiously unaffiliated. We expect to publish those projections in 2013.

The primary researchers for “The Global Religious Landscape: A Report on the Size and Distribution of the World’s Major Religions as of 2010” are Pew Forum demographer Conrad Hackett and senior researcher Brian J. Grim, the Pew Forum’s director of cross-national data. They received valuable research assistance from research analyst Noble Kuriakose and other Pew Forum staffers listed on the masthead of this report. We are also indebted to our colleagues at IIASA, Marcin Stonawski, Vegard Skirbekk and Michaela Potančoková, and to Guy Abel at the Vienna Institute of Demography.

While the data collection and analysis were guided by our collaborators, the Pew Forum is solely responsible for the interpretation and reporting of the data.

Luis Lugo, Director Alan Cooperman, Associate Director, Research