Finding stats 101
So, you need statistics for your research. There are lots of place to look for stats, and this guide will help you.
Bear in mind though that statistics can take some digging to find, and that what you want numbers for hasn't necessarily been counted yet. One further point - almanacs, handbooks, encyclopedias, websites like that of the census etc., all can be helpful, but keep in mind that a good book or article on your topic may well be an excellent source of numbers - maybe they did the digging for you!
General International Stats
General US Stats