Comscore undercounts Firefox

Self-explanatory.

5. Firefox and Safari. We knew that Comscore’s toolbar did not work on Safari, and therefore did not count the typically sophisticated users of the Apple Mac internet browser. But I hadn’t realized how much Comscore undercounted usage of Firefox. The Mozilla browser is used by about 15% of the US internet population; Firefox devotees account for only 7% of Comscore’s panel, according to a publishing exec who has spoken recently with the firm.
So, what does that mean? Well, a site viewed, hypothetically, only by Safari users, would show as having no audience at all. A site with only Firefox fans would register with about half the audience it should. A normal tech site? The audience for Lifehacker, Gawker Media’s software and productivity title, is about 60% Firefox, 5% Safari, and 30% other. Assuming Comscore doesn’t take account of its undersampling of geek browsers, that factor alone would cut Lifehacker’s measured audience by 33%. And that’s compounded by the more general problems with Comscore that MSNBC.com and other big internet publishers are complaining about.

STATS: How Comscore kneecaps Silicon Valley startups – Valleywag