If I sold something on the Internet, then I would say I'm open to the international market. Now, out of 6 billion people on the planet, how many people actually own a computer, are connected to the Internet, and have access to a credit card or bank account?

This isn't exactly the straight-forward answer you may want, but it may help a little.

Linky to article

Well, yeah, there's gotta be more than 15 million people out of 6 billion. :)

The linky just gives VISA transactions..just as many, if not more (I haven't a clue) may use mastercard or whatever other transaction names there are instead of VISA.

If I use some common sense and eliminate the poorest continents and countries,
then I would say the number is actually less than 10% of 6 billion, 600 million or less.
Probably even half of that too, 300 million at best. 5% of 6 billion still good I suppose.

Isn't a more relevant question "How many of these people are interested enough in my game to purchase it?".

I personally love wargames. Unfortunately for those who make them, I am in a vanishingly small minority of those who can spend money on the internet. (~25000)

Yeah, I could look at the problem from both sides, but ultimately, there is only so many
people on the planet, so I like to think big. if only I could reach every single one. :)