What is the magnitude of Satanism on our world?

...and how sure of your answer are you?

Bogus religion. Middle age nonsense.

Which type?

666

LaVeyan satanism is likely...maybe 1,000,000 strong, including all the members of the Church of Satan, independents, and smaller groups. I guess it would include wish-washy satanists too

Add another 10,000 for other forms of satanism, maybe as much as 20,000

As grave as the illegitimacy of piracy against Spanish Gold ships of the olden days. My answer is definite as the St. Peter's Basilica in Vatican City: very artistic, grand and marvelous.

I'd say between 15,000 and 20,000 adherents worldwide.

But in an attempt to be more hard-nosed about it, I will crunch numbers for you and give you a couple of (most likely unreliable) figures.

Here we go:

1,525 Satanists were counted in the UK 2001 Census.

In a nation of 58,789,194 people, that equals roughly 0.0026% of the population.

The world's current estimated population is a little over 6.7 billion.
0.0026% of 6.7 billion is 17,420,000. However, since much of the world is illiterate (or just too poor to afford Internet access and books) and Satanism is primarily spread through documents in English and other European languages, this is a heavily inflated number.

307,458,667 + 499,673,300 + 4,143,279 + 21,910,583 = 833,185,829
(U.S. population + EU population + NZ + AU = total population of areas with significant Satanist population)

0.0026% of 833,185,829 is 2,166,283.

So, the number of Satanists worldwide could be somewhere between around two million. But personally I think it's probably really only in the tens of thousands.