Christendom comprised mainly of Roman Catholics and Pentecostals

Finnish theologian and Fuller Theological Seminary professor, Veli-Matti Karkkainen, who interestingly was sent back to Finland (yet now has returned) after 9/11, mentions these remarkable statistics in regards to denominations in Christendom:

"If currently Roman Catholics are the largest Christian group, then classical Pentecostals are now the second largest and gaining fast. Catholics now number about one half of all Christians, while Pentecostals make up almost a quarter." (An Introduction to Ecclesiology, 69)