[thebelal]

The axis are described in the text

> The x axis (log scaled) gives the number of speakers (plus one, so as not to make dead languages fall off the scale). The y axis, also log scaled, shows the adjusted wikipedia size.

As is the real ratio

> real ratio, defined as the number of ‘real’ pages divided by the total page count

Not sure why they couldn't put the above in the figure legend (or better yet label the plot directly). I agree it is poorly done.