Neither Gartner nor IDC—the Pepsi and Coke of computer forecasting—ever admits to mistakes. Which is what makes this chart (enlargeable version below) so interesting.
Assembled by Charles Arthur, long-time British tech editor (Independent, Guardian) it shows—more definitively than I’ve ever seen—the awesome magnitude of those mistakes.
In June 2011, for example, IDC forecast 2015 sales of 540 million PCs, way more than—nearly double in fact—the 276 million PCs that were actually sold that year.
IDC’s 2011 prediction for tablet sales was just as far off in the other direction. What were forecast to be unit sales of 100 million in 2015 came in, according to IDC’s final estimate, at 207 million.
Click to enlarge.