Thanks for pointing that out! This is a preliminary report, so there are many questions this report doesn’t answer yet. We know that compared to the total exit relay traffic the number of complaints is probably pretty negligible and we will take that into account in final report.
From your answer I assume you think I was trying to say "but the abuse rate is quite low for that kind of bandwidth" - I was not trying to say that.
What I was actually trying to point at was: Since the number of abuse emails significantly increased over time an uneducated guess would be "oh tor abuse is increasing", but I rather think that torservers' ressources increased over time - which allowed them to: 1) push more traffic 2) get better hosting with allowed them to run a more open exit policies
If such things would be reflected in these graphs potential exit operators probably wouldn't assume that over time they will get more complains.
Such over time graphs should probably only be made for a static (non-changing) exit policy (so you would have to draw per-exit graphs with probably shorter time-spans).