score:3
This is the most comprehensive survey (dated December, 2011) that I could find. You will need to examine this lengthy report yourself for more detailed information but the following extracts may be useful:
About half of all Christians worldwide are Catholic (50%), while more than a third are Protestant (37%). Orthodox communions comprise 12% of the worldβs Christians. Other Christian groups, which make up the remaining 1%, include the Church of Jesus Christ of Latter-day Saints (Mormons), Jehovahβs Witnesses and the Christian Science Church. Muslims, the second-largest group, make up a little less than a quarter of the worldβs population http://www.pewforum.org/2011/12/19/global-christianity-traditions/
The following link provides information on how Catholics, Protestants, Orthodox and other denominations are categorised: http://www.pewforum.org/2011/12/19/global-christianity-traditions/#defining
Here is a brief statistical summary from the findings within this report:
Total Christian Population Worldwide: 2.184 billion (31.7% of world population)
Of which: Catholic 50.1% Protestant 36.7% Orthodox 11.9% Other 1.3%
Within Protestantism: 305 million Charismatics 279 million Pentecostals 285 million Evangelicals
Largest Distinct Protestant Denominational Families: Anglican (11%) Lutheran (10%) Baptist (9%) Reformed/Presbyterian (7%)
Total Muslim Population Worldwide: 1.6 billion (23.4% of world population)
Certainly, this report gives "ballpark" estimates about the largest groups within Christianity. It is possibly the most detailed and comprehensive survey available, even though these statistics are 8 years old. I hope this helps you.