Ohh reasons to be at certain levels sure would be interesting.

This chart appears to be total toons at each level, which of course, would show more toons at the beginning levels and at the parking levels (pvp levels, easier levels, (previous) level cap levels).

It might be interesting, as someone as previously pointed out, to see toons that are active daily or weekly for x hours per day/week, just to see where the real activity is.

There will always be more toons at the lower levels though, due to parking and to people beginning the game and moving on or taking a break, etc etc.