It's not just that it's because they manipulate the numbers from year to year. For a long time they referred to the fseries as the best selling. Now it's the F150. My favorite thing is that more Chevy pickups are on the road today than any other brand.

 

I've always been told, even through print magazine, that the Chevrolet and GMC models are counted separately. So that's why the Ford F-150 or F-Series is the best selling for all those years.

I haven't crunched the numbers from every years sales figures, but I'm sure the Ford deserved it's total win more than a year or two, but I wouldn't be surprised to see the GM trucks at the top in combined sales...seeing as how they are the same models.