The sales are an extrapolated global estimate based on the sales figures tended by about 55 leading chip companies.
Intel and AMD both withdrew cooperation from WSTS (http://www.eetimes.com/electronics-news/4237197/Intel--AMD-leave-WSTS). As far as I know they have not resumed membership.
Hi Peter - back calculating the actual January sales from the SIA published 3MMA sales number, quoted in your article above, yields $22.804 billion. Plugging this actual sales result into the Cowan LRA Model yields an overall 2013 sales forecast of $310.402 billion which corresponds to sales growth expectation of 6.5 percent. These two results are preliminary pending the official release of January's actual sales by the WSTS - expected by the end of this week, that is March 8th. Once the January actual sales is published the Cowan LRA Model will be rerun and 2013 quarterly sales numbers will also be derived