The Pew Research Center scored ample ink at GetReligion and elsewhere with its important April report on global trends that all religion writers will want to keep on file: “The Future of World Religions: Growth Projections, 2010–2050" (.pdf file here). The 245-page publication provides religious population estimates as of 2050 for each of the 198 nations and territories that have  populations of 100,000 and above, by calculating such factors as birth rates, age distribution, migration, life expectancy and  rates of switching between religions in 70 nations for which we have data.

The headline item was the Pew team’s estimate that “by 2050 there will be near parity between Muslims (2.8 billion, or 30 percent of the population) and Christians (2.9 billion, or 31 percent), possibly for the first time in history.” (Pew explains that Muslims might have outnumbered Christians sometime between 1000 and 1600 as Muslim forces repeatedly invaded Christian strongholds and the Black Death decimated Europe. But we’ll never know because estimates for the Middle Ages are “fraught with uncertainty.”)

The most significant response to Pew’s report (.pdf file here) comes from another essential resource for journalists, the Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary.  That analysis tapped the annual CSGC survey for the International Bulletin of Missionary Research, which was expanded this time to include projections to 2050 (.pdf file here).  This center, which the Religion Guy recently visited, provides statistics for various reference books and has just began work on a 3d edition of its World Christian Encyclopedia.

As of 2050, CSGC projects a slightly lower global count than Pew for Muslims at 2.7 billion, and a considerably higher 3.4 billion for Christians.

Why the disparity? Both agencies track established demographic censuses and surveys, but CSGC also considers statistics from  religious denominations themselves.  In addition, CSGC relies upon observers it has recruited in each nation to assess “non-traditional forms of Christianity” that achieve “some of the most significant growth of Christianity in the world today.” This includes “house churches and insider movements (where individuals convert to Christianity in secret and/or remain identified with their past religion).”

China and India are of particular importance. The center says that in nations like this that have “high governmental and/or social restrictions on religion,” believers “often do not report their true religious affiliation in order to avoid persecution.”  Thus, CSGC draws from “on-the-ground contacts” who say Christianity is expanding through conversions and underground communities. Pew does not calculate religious switching in either nation, cautiously citing the lack of reliable data.

Pew figures by 2050 China will be  5.4 percent Christian and India 2.2 percent whereas the CSGC projects roughly triple that, 15.8 percent and 6.9 percent respectively,  a difference of nearly a quarter-billion souls. CSGC “consistently finds more switching to Christianity in many African and Asian countries” than Pew does. In 35 years we’ll know whether Pew’s standard demographic data or CSGC’s added reliance on church insiders comes closer to the mark.

Here are the CSGC current estimates by category: Christians (all kinds)  2.4 billion, Muslims 1.7 billion, Hindus 985 million, Buddhists 520 million, Chinese “folk religionists” 454 million, “ethnoreligionists” 260 million, “new religionists” 65 million, Sikhs 25 million, Jews 14.5 million, and agnostic or atheistic “nonreligionists” 831 million.

Reporters note: Pew’s director of religion research is respected former Washington Post religion writer Alan Cooperman (202–419-4372); he or Pew’s media staff can be e-mailed via  www.pewresearch.org. Gordon-Conwell’s expert is Todd M. Johnson and his center fields media inquiries sent to info@globalchristianity.org. The CSGC office is at 978-468-2750.