The key word here, of course, is "retail." In fact, the real headline here should be "NPD data becomes 14% less relevant in regards to measuring the relative success or failure of the PC gaming industry," but we pay the guy who carves the headlines into the site by the letter. For what it's worth, here's the number: PC games brought in $701 million at retail last year.
As you know, that doesn't account for Steam, GoG or any of the many other platforms of digital distribution currently making up an increasingly large segment of PC game sales. As it stands, we're more inclined to report that 14% fewer people like owning boxes.