Are Zooms Always Sharper at One Extreme or the Other?

There is a statement often repeated about zoom lenses, which I have assumed to be generally true, or at least historically true. “All zooms are sharper at one end than the other.” I also hear a lot of people saying they bought Zoom A because it’s sharper

via LensRentals Blog: http://www.lensrentals.com/blog/2011/11/are-zooms-are-always-sharper-at-one-extreme-or-the-other

Like most photographers, I understand things better when I can see them, rather than just read about them. So I thought I’d use some of our Imatest data to look at this well-known truth (which isn’t as true as people seem to think). I’ll also provide you some links where you can find more specific data concerning how much zoom resolution varies with focal length.