I was invited to join into a Nielsen/NetRatings panel. This is like the Nielsen ratings where they put a box on your TV to see what you are watching. In this case they put some software on your computer to see where you go on the internet for a month. But when I went to sign up I was told:

We’re sorry, but currently our program is only available for PCs running Microsoft Windows 95 / 98 / Millennium (Me) / NT4 / 2000 / XP. However, we may be launching our offer for Apple Macintosh and / or different Operating Systems very soon.

So don’t be surprised if you see Niesen/NetRatings claiming that the percentage of computers on the internet that are Macintoshes has fallen to 0%. You cannot measure what you refuse to see.