After its birth in Asia, Christianity had its most vigorous growth as it moved steadily westward and northward. As more and more people in the West embraced Christianity, the statistical center of gravity moved north and west. However, beginning in 1900, the statistical center began to dramatically shift southward, and in 1970 it began to move eastward for the first time in 1,370 years! Today, the statistical center of Christianity is located in Timbuktu! This means that for the first time since the Reformation, the majority of Christians (approx. 67%) are now located outside the Western world.
-Timothy Tennent, Theology in the Context of World Christianity