The article is talking about online market share, i.e. percentage of browsers going to websites, not percentage of new computers purchased in the marketplace.

I work for an e-commerce site that seems to track the average pretty closely. Windows as a whole is at 91.09% of our browsers, of which 74.09% is XP and 23.51% is Vista. Mac is at 7.98%. Last November, that number was 5.87%, which is a 35.9% increase in total Mac browsers in 1 year! In the same period, Linux has gone from 0.41% to 0.62%, an increase of about 51.2%