Stupid Variance Question

[SGspecial]

I know there are no stupid questions, but this one should be absurdly easy to answer for someone who knows statistical analysis. I want to compute the variance of a population of EV samples, many of which have the same value. For example, I have 1000 samples: 412 of them are -2, 307 of them are -4, 211 of them are -6, and 70 of them are 0 (zero). What's the easiest way to compute the variance of this population?

p.s. Jerrod and Bill, if you're out there, just let me know if this is already in your book and I'll go out and buy it. Well, the 2nd edition anyway.