Be sure to look at the numbers in the charts. Those bars there don't use the full axis and suffer from distorsion. It's the #1 don't in the list at http://www.eea.europa.eu/data-and-maps/daviz/learn-more/char...
In one example we're talking a visual difference of >50% which amounts to an actual difference of 80 "points" out of 10000, so <1%. (No, that's not a typo on my part.)
You have to wonder of most of the visual difference isn't actually just statistical noise at that point.
Firefox: 10,000
Chrome: 9,940