With sales falling 10.6 percent this past quarter, the PC industry experienced the biggest drop in sales in its history, according to the market research firm IDC. Competing research firm Gartner is painting a nicer picture for the industry, putting the decline only at 8.3 percent. Despite the introduction of Windows 10 and the holiday season, worldwide PC shipments stayed under 300 million units for the first time in seven years, according to both firms.

The IDC points to a number of issues that kept the PC market down, including competition from smartphones and tablets, weak international currencies, and even blaming the free Windows 10 upgrade program as a deterrent for users who bought new PCs in 2014 from buying new machines in 2015.

Mac sales keep outpacing the rest of the PC industry

But none of those issues have affected Apple, which has kept growing its Mac sales despite declines in every other aspect of the PC industry. Apple is now the third largest PC maker in the US, passing Lenovo, according to both Gartner and IDC. Worldwide, the firms differ on Apple, with the IDC placing them in fourth place, while Gartner places them in fifth.

Despite the declines in 2015, both firms believe the PC industry will rebound somewhat in 2016, thanks to commercial adoption of Windows 10 and an accelerated consumer adoption cycle from PC users who haven't upgraded to Windows 10 yet. "We continue to believe that a majority of these users will purchase another PC, motivated by new products and attractive pricing," the IDC wrote. "Commercial adoption of Windows 10 is expected to accelerate, and consumer buying should also stabilize by the second half of the year."