How old is that graphic OS X 10.9 has been somewhere around a year...
http://www.fool.com/investing/general/2014/07/08/apple-incs-us-market-share-not-the-problem.aspx
Not sure how old.
I posted it just to show that Apple's desktop percentage is very low. Yes, all the beautiful people have the glowing Apple logo displayed when they open up their laptop and Apple fans are even more loyal and vociferous than Green Bay Packer fans, but the actual percentage of USERS is very low.
IF Apple could run the good CAD programs and IF their prices were competitive then I might consider the hassle of teaching this old dog a new OS. However, the last time I tried was 20 years ago and I decided that it was NOT worth the effort.
Kinda like Windows 8...
:-)