I recently started using Quantcast on my site to determine my audience (which, really the site is so small now that I already know). When I look at some of the metrics on Quantcast, I see gender, education level, etc. How does quantcast determine these? Are they relatively accurate (I'm sure they are more accurate for a large site with more data to draw from). Does it determine this from tracking IPs across my site and others? What's going on that gives them enough data to even begin to give a metric on something like education level?