Seriously, this is possibly the best mathematical model EVAR. Some geek made an actual mathematical model of the ecology of vampires and humans. Someone had said that if vampires live forever, they would eventually populate the planet out of control and exhaust their food source (humans). Of course, that then led to the fact that because we are not overrun with vampires, there MUST be a Slayer.
Here's the math:

Basically, it all calculates out to show an equilibrium population of 36,346 humans and 18 vampires as long as a person slays the extra vampires. Interestingly enough, the established population of Sunnydale on the show is 38,500 humans, pretty damn close to the equation result. So, because we are not neck-deep in starving vampires, clearly we are living in the Buffyverse. Proof again that Joss Whedon is a GOD, and that Stephenie Meyer is an idiot.
Read more HERE and HERE.
Here's the math:

Basically, it all calculates out to show an equilibrium population of 36,346 humans and 18 vampires as long as a person slays the extra vampires. Interestingly enough, the established population of Sunnydale on the show is 38,500 humans, pretty damn close to the equation result. So, because we are not neck-deep in starving vampires, clearly we are living in the Buffyverse. Proof again that Joss Whedon is a GOD, and that Stephenie Meyer is an idiot.
Read more HERE and HERE.