As PC sales head to Hades and Windows 8 adoption numbers totally discombobulate, brace for PC doom and gloom over the tide of Yule IDC is out with its latest PC shipment prognostications for 2013, and the number’s aren’t good. IDC expects worldwide PC shipments to decline 10.1 percent in 2013 compared to 2012. That’s “by far the most severe yearly contraction on record,” but it’s only part of the story.NetMarketShare’s combined Windows 8 and 8.1 Internet usage numbers climbed from 9.0 to 9.3 percent between October and November, an anemic showing at best — but that, too, is only part of the story. The PC market is getting hammered hard and as best I can tell, 2014 will be worse — much worse.Let’s reset the system clock. In early March I took a look at the then-current predictions for PC shipments in 2013, when IDC stated: A few months ago, IDC was predicting a 2.8 percent increase in worldwide PC sales for 2013. Three months later, the prediction now stands at a 1.3 percent loss.Nine months later, IDC is predicting a 10.1 percent decrease in worldwide PC shipments for the year. It’s worth noting that IDC made the prediction of a 1.3 percent decline when it already had three months of data to work with. (In the same article I said, “it wouldn’t surprise me a bit to see double-digit declines, year-on-year, for desktop and notebook PCs.”)Now IDC predicts “Total shipments are expected to decline by an additional 3.8 percent in 2014 before turning slightly positive in the longer term.” If you believe that, I have a bridge in Brooklyn in need of bidders.Three weeks ago Gartner predicted that fourth-quarter PC shipments in 2013 will be 3 percent lower than in 2012, and the PC industry is “nearing bottom.” I say they’re dreaming. We haven’t even started to hit bottom. Every indication I see says that Windows 8 is crashing and burning — and dragging the PC market down with it. It wouldn’t surprise me a bit to see another double-digit fall in PC shipments for 2014. (Unless IDC and Gartner start re-defining the term “PC,” in which case everything’s made up and the points don’t matter.) Remember, we’re talking about shipments, not real sales net of returns — a number that would be much more interesting and probably more frightening.Putting all anecdotal evidence aside for the moment, Windows 8’s tumultuous belly flop couldn’t be better demonstrated than in the statistics just released by NetMarketShare. Yesterday, Serdar Yegulalp explained — quite correctly — that the tiny bump in Windows 8 and 8.1 Internet usage between September and November isn’t all that unusual historically. Windows XP, for example, grew at a similarly somber rate at that stage in its development.But the numbers don’t add up … Roughly 350 million PCs were shipped worldwide in 2012, according to IDC, with 315 million projected for this year. While the monthly shipment data isn’t available, it’s reasonable to assume that 20 million-or-so PCs shipped in October and a similar number in November. In theory, every new PC that’s sold ships with Windows 8, although Software Assurance licensees can request Windows 7. So the bump in Windows 8 and 8.1 by a mere 0.3 percent usage points represents the combined effect of 40 to 50 million new PCs going into service over those two months. No matter how you slice it, that isn’t possible — unless Windows 8 users are boycotting the Internet en masse.The discrepancy arises because a) many companies don’t want Windows 8, b) many PC manufacturers in many parts of the world don’t ship new machines with any operating system, and c) many owners of new PCs install Windows 7 — legit or pirate version — as quickly as they can. That’s why Windows 7 usage is up marginally.Perhaps IDG and Gartner are right and the Grinch will spare Windows Whoville this Christmas. Perhaps we’re in for a tiny decline in 2014, in preparation for a return to a pre-2008-style uptick in PC shipments by 2017. Somehow, I doubt it. Oh, the Who-manity.This story, “Look for the Windows 8 Grinch this holiday season,” was originally published at InfoWorld.com. Get the first word on what the important tech news really means with the InfoWorld Tech Watch blog. For the latest developments in business technology news, follow InfoWorld.com on Twitter. Software DevelopmentTechnology IndustrySmall and Medium Business