Confusingly, by default, the graph is on a logarithmic scale. You can change it to a linear one, try it and see; it looks like its growth is constant. Although

Confusingly, by default, the graph is on a logarithmic scale. You can change it to a linear one, try it and see; it looks like its growth is constant. Although I too would like to think we are converging towards having cataloged all knowledge, if Wikipedia's growth is slowing down, I'd bet it's because of all of its bureaucracy.