The big, big problem with such charts is that the vertical thickness <i>perpendicular to the x axis</i> of the line is the actual proportion, but your brain will look at the thickness perpendicular to the gradient.<p>To put it visually: <a href="http:&#x2F;&#x2F;i.imgur.com&#x2F;vZ7uTu1.png" rel="nofollow">http:&#x2F;&#x2F;i.imgur.com&#x2F;vZ7uTu1.png</a><p>The pink bars are the percentage market share as your brain reads it. The green bars are the percentage market share the graph is supposed to show. (The burning sensation in your eyes is because I made a poor choice of colours.)<p>If you were to naively look at the thickness of the black area (shown with the pink bars), it&#x27;d look like it was constant. But look at the vertical height (green bars): whatever this proportion is, the black has started small, grown massively, then contracted.