(From top to bottom: September 2008, first half of 2008 and first half of 2007)

Warner Music Group had a good September -- even though overall sales were atrocious compared to both September 2007 and the entirety of 2008. So good, actually, that WMG overtook Sony BMG for #2 in album market share. WMG shot up to 24.7% and Sony BMG dropped to 21.6%. Universal Music Group still dominates with 32.4%. EMI had 9.4% (the same share it had in the first half of 2008) and all others split up the 11.9% remainder.

September marked the latest phase in Sony BMG's fading market share. WMG had 20.8% in the first half of 2008 and 20% in the first half of 2007. Sony BMG had 24.8% of album sales in the first half of 2008 and 25.3% in the first half of 2007. (Ed Christman's July 2 article at Billboard.biz has the stats. Here's a link to a spreadsheet with the numbers.) At the time of the merger, Sony and BMG had a combined 29.78% album market share.

Of course the entire market is falling, but there's a big difference between losing sales and losing market share. The latter can be controlled by any one company -- they either take it or cede it to competitors. The former, a falling album market, is less influenced by any one company. In 2008, each percentage point of album market share lost is equal to about 3.8 million units. At an average wholesale cost of $9 per unit, that's about $34 million in revenue.