Ah, you're a Mac user. You can't go in there. Mac users in particular make up an extraordinarily high percentage of Internet users in comparison to the percentage of Macs in use. This is mostly because the Mac has always made getting onto and using the Internet so easy. To exclude the best selling computer on the market simply because it runs a different operating system is ridiculous.
People pick their operating system for many reasons.
In a sense, they are more important than the general masses simply because they are non-standard. If you look through the history of the world, significant change was always caused by a small percentage of the people. To exclude their views on something as impactful as the Internet is criminal. Normal Nielsen studies include a statistical amount of these people automatically by accepting people from a wide range of society. But Nielsen's net ratings service is inaccurate and does a grave disservice to society and the Internet as a whole by excluding entire groups of individuals from their studies.