Preface

This report focuses on the size and geographic distribution of the world’s Christian population as of 2010. It is, in that sense, a snapshot in time. But because the true picture is not static, the Executive Summary also presents some comparisons with the world’s Christian population a century earlier. This is far enough back in time to allow us to see substantial change, yet not so far back that the population figures become hopelessly murky.

The estimates for 1910 come from a leading expert in the quantitative analysis of historical data on Christian groups, Todd M. Johnson of the Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary in South Hamilton, Mass. Dr. Johnson and his colleagues at the Center for the Study of Global Christianity also provided the estimates for the size of global Christian movements (such as pentecostalism and evangelicalism) and Protestant denominational families (such as Baptists and Methodists), which are based primarily on church membership statistics.

All the other demographic data in the report – including the estimated number of Christians in each country and region of the world in 2010, as well as the breakdowns of those figures into Catholics, Protestants, Orthodox and other Christians – were compiled by the staff of the Pew Research Center’s Forum on Religion & Public Life and are based primarily on censuses and nationally representative surveys. For the European estimates, the Pew Forum’s demographers worked in close collaboration with researchers at the International Institute for Applied Systems Analysis (IIASA) in Laxenburg, Austria.

This effort is part of the Pew-Templeton Global Religious Futures project, which analyzes religious change and its impact on societies around the world. Previous demographic reports produced under the Pew-Templeton initiative, jointly funded by The Pew Charitable Trusts and the John Templeton Foundation, include Mapping the Global Muslim Population: A Report on the Size and Distribution of the World’s Muslim Population (October 2009) and The Future of the Global Muslim Population: Projections for 2010-2030 (January 2011). Gradually, we hope to publish estimates for the current size of other major religious groups, including the unaffiliated, as well as to project their growth rates into the future.

Readers should bear in mind that the definition of Christian in this report is very broad. The intent is sociological rather than theological: We are attempting to count groups and individuals who self-identify as Christian. This includes people who hold beliefs that may be viewed as unorthodox or heretical by other Christians. It also includes Christians who seldom pray or go to church. While this report does not make any attempt to measure what Christians believe or how they practice their faith, the Pew Forum has conducted and will continue to conduct numerous other studies that look closely at the beliefs and practices of Christians in the United States and around the world.¹ 

The primary researchers for Global Christianity: A Report on the Size and Distribution of the World’s Christian Population 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 Noble Kuriakose and former Pew Forum research assistant Andrew J. Gully as well as other staff members listed on the masthead of this report. We are also indebted to Todd Johnson and to our colleagues at IIASA, particularly Vegard Skirbekk, Marcin Stonawski and Anne Goujon. We would like to thank Elizabeth H. Prodromou of Boston University and Alexandros Kyrou of Salem State University for sharing their deep knowledge of Orthodox Christianity. And last but not least, we are grateful to Timothy Samuel Shah of the Berkley Center for Religion, Peace, and World Affairs at Georgetown University for his many contributions to this report, particularly the country profiles and definitions of various Christian traditions and movements.

Luis Lugo, Director
Alan Cooperman, Associate Director, Research  

Footnotes: 

1 See, for example, the Pew Forum’s U.S. Religious Landscape Survey (2008), Spirit and Power: A 10-Country Survey of Pentecostals (2006) and Tolerance and Tension: Islam and Christianity in Sub-Saharan Africa (April 2010). The two international surveys were also part of the Pew-Templeton Global Religious Futures project. (return to text)