If you go thought the process of buying an ad, you can see statistics on the users of facebook. These are some that I found interesting. If you don't know, "k" means thousand, and "m" means million. These stats are mostly for North America.
Total users in Canada is about 15.7m, or about 50% of the population (highest % that I found).
There are 123m users in the USA, which is about 41% of their population.
The UK has about 26m accounts listed, which is about 42% of their total population.
Together, thees three countries alone account for 41% of all facebook users (164/400 m).
Want to advertise to males in the US over 18? That's 48m possible customers. What about women over 18? That's almost 60.9m.
In general, there are more women than men on facebook.
600k men who live in North America are listed as being interested in men. Out of a total 66m men; this is under 0.01%. 2.5m women in North America are listed as being interested in women. Out of a total of 81.6m women; this is 3%.
Most people say that about 10% of the world is homosexual. This doens't agree with facebook, however, that's not much of a surprise.
23.7m men in North America are in some kind of relationship. 35.4m women are listed as being in some kind of relationship. 12m is a pretty big difference. 32m people are listed as single.
93m people are listed as either single or some kind of relationship, out of 151m total in north America.
21.7m people say they are between the ages of 13 and 18. 47% are male, 53% are female.
More than 2m people in NA say that they like video games.
11m people live in Mexico. That is 9.9% of their total population of 111m.
DISCLAIMER:
This is not 100% right, because it is based on what people have listed in their profiles, which may not be true. Some user might also have two accounts, and some are not active.
