I heard this has more market share than windows, *nix etc. put together and then multiplied by a really large coefficient.
EDIT: p.s., I don't believe that graph for a second. For instance I reckon they only started including non-PC devices from 2005 (otherwise a lot of iPhones and "others" were sold effectively overnight). It's also interesting to see how Apple's growth from 2005 has been somewhat slow and how Microsofts growth is going up again. But statistics, you can make them say anything. Especially if you do them badly.