Ed Stetzer of Wheaton College (Illinois) furrowed many a brow with an April 28 Washington Post warning that “if current trends continue” without letup, Americans active in “Mainline” Protestant churches will reach zero by Easter 2039.

Talk about timing.

That bleak forecast – mitigated by U.S. “Evangelical” Protestants’ relative stability – comes in the 500th anniversary year of the Reformation. This massive split in Christianity was sparked by a protest petition posted by 34-year-old German friar and professor Martin Luther on All Souls’ Eve (October 31) of 1517.

The Protestant scenario is rosy at the world level, however, according to anniversary tabulations by the Center for the Study of Global Christianity (CSGC) at Gordon-Conwell Theological Seminary, a standard resource for statistics and trend lines from 1900 to the present (media contact here).

Director Todd Johnson scanned the situation for Stetzer’s blog at ChristianityToday.com with a 500-year infographic summary (.pdf here).

The CSGC anniversary report is especially useful because Pew Research Center’s comprehensive April update on world religions had numbers for Christianity as a whole but did not break out the Protestant segment. Pew does offer an estimate that 37 percent of the world’s Christians are Protestant if you include Anglicans and the burgeoning “Independents” in the developing world.

CSGC counts Anglicans as Protestant but treats the Independents, non-existent until the 20th Century, as a new, large, expanding and separate Christian branch from Protestantism. Despite some similarities, such churches lack direct ties with historic Protestant denominations.

From its 1517 start, Protestantism grew to claim 133 million followers in 1900, nearly doubled that by 1970, and more than doubled again to reach an estimated 560 million this year, with a projected 626 million by 2025. The faith exists in nearly all the globe’s 234 nations and territories.