> NetMarketShare's stats are more accurate than any of the others listed there
On every site I've monitored (none of which cater to technical users, one of which is aggressively non-US-centric), NetMarketShare's stats wildly inflate IE's market-share, particularly internationally. That's not to say that they're fictitious but rather that they reflect a certain viewpoint and methodology which is only relevant for a few customers. I've found Akamai's numbers to track very closely with what I measure:
http://www.akamai.com/html/io/io_dataset.html
They don't publish technical details about their methodology but I suspect you're seeing a sampling bias: NetMarketShare is used by a modest number of large companies, almost exclusively North American and mostly related to media, and their stats appear to depend on an embedded JavaScript tracker:
http://netmarketshare.com/faq.aspx#Methodology
There are some apparent technical botches: they didn't appear to use a CDN at all — when I last traced counter.hitslink.com in the spring everything went to Los Angeles and was correspondingly slower globally but it now[1] appears that they might be using CloudFront — or set Cache-Control headers, so if you're outside North America or on a slow connection you were going to see a higher rate of their JS failing to load and for the tracker ping back not to load by the time the user navigates to a new page:
http://redbot.org/?uri=http%3A%2F%2Fcounter.hitslink.com%2Ft...
(In contrast, the Akamai numbers reflect direct HTTP traffic for sites like microsoft.com, iTunes, etc. so they avoid the issues related to JS trackers but do require care to filter robots which spoof a browser UA)
They also listed some major sites like CNN or Mozilla which didn't use that JS bug so they either have an unadvertised bulk log delivery service or are portraying smaller side sites as representative of the massive high-traffic main sites.
The real question is the way they interpret the data, and in particular the weighting scheme. Because “everyone knows” Internet Explorer is common in China, they weight the numbers to represent this but you're simply hoping their usage of the CIA Internet Traffic by Country report is accurate:
http://www.netmarketshare.com/faq.aspx#Country
The numbers I can measure are very close to Akamai, showing Chrome tied with IE even in China:
http://www.akamai.com/html/io/io_dataset_v2.html#stat=browse...
1. http://www.webpagetest.org/result/131107_2C_PZK/1/details/