IDG Contributor Network: Why did Mac sales decline 10% in 2016?

Mac users have not been very happy with Apple lately, and it showed in the company’s 2016 sales numbers for the Mac. Mac sales declined by about 10 percent while Apple’s Windows-based competitors gained some ground at Apple's expense.Michael Potuck reports for 9to5Mac:
It’s not surprising that Mac sales dropped for Apple in 2016 as they experienced their first year over year sales decline since 2001. What is interesting, however, is that as Mac sales dropped roughly 10 percent