http://marketshare.hitslink.com/operating-system-market-share.aspx?qprid=8
You may also want to try actual numbers.
The figures you are reporting are WORLD "market" share... this article is about US "Market" share. But what your reports are counting are "non-unique machine" hits on specific websites... not computer sales... or market share. They just give you the number of machines that click on the websites that use their counters.
You might want to use US market share rather than the skewed figures of Netmarketshare, which reports on 90,000 Windows centric websites... and who also started putting in guesstimates last year, based on two and a half year old CIA fact book data estimates of PC computer usage in China because they can't get real numbers... distorting their reports.
However, GARTNER'S reports have remained consistent and are based on actual shipments of computers and are NOT BASED on visits to internet websites. They are HARD numbers... not wishy-washy hit counters.