The 33000 comes from Barrett, et al World Christian Encyclopedia (2001 2nd edition). As pointed out in other threads on this topic, the source breaks it down this way:
Denominations / Paradenominations:
These are total “Christian” “denominations” including Roman Catholic, Orthodox, Protestant denominations, independent groups, and pseudo-Christian sects, cults, and “marginal” groups who claim to be in some sense “Christian.” Now we know 99% of these are Protestant. How do we know that? Well, if you claim to be “Christian” you are either (1) Catholic, (2) Orthodox, (3) Protestant.
Let’s deal with (1). Barrett claims there is one Roman Catholic Church for each country. In other words, the RCC of the United States is a totally different denom than the RCC of Canada, etc. That’s bogus, but we’ll give him this. So here Barrett counts “242 Roman Catholic denominations.” OK, subtract 242 from the total we get:
33820 - 224 = 33596.
That still leaves 33000+ Protestant and “Orthodox” denominations. Now subtract (2). Barrett counts “781 Orthodox denominations.” That leaves us Protestants only:
33596 - 781 = 32815
For a grand total of 32815 Protestant denominations, whether they call themselves “Anglican” or “independent Christian” really doesn’t matter. If you aren’t Catholic or Orthodox, you are Protestant. You round this number up, and you still have the dreaded 33000 figure. Sorry but just thought I’d defend the number again in light of White’s challenge on his blog.
So yes, Steve Ray and Tim Staples and all those apologists using the dreaded 33000 number should repent of this lie if they want to be precise. They should actually use the number 32,815 Protestant denominations. Hey it’s a Protestant source published in an updated edition by Oxford University Press: World Christian Encyclopedia (2001 edition) by David B. Barrett, George Thomas Kurian, Todd M. Johnson. So we’re not talking a poll taken by Chick Publications or something.
How Many Protestant Denoms are There?