Like you I think this is pretty important information, so I worked it out for myself to have some demographic guidelines for the games I run. These numbers are not official, but based on extrapolating from official information. And more importantly I'll explain how I got to those numbers, so you might be able to get some use of it even if you don't agree with every one of my assumptions:

First, there's a total population of 71-72 thousand vampires worldwide (counting Laibon as Kindred, but discounting Kuei-Jin). This is more or less canonical information, although it's a little outdated...