I don't understand what that graph is showing. Which variable is independent, or supposed to be? It can't be buckets as a function of collisions. At first I thought he had his axes reversed (from the customary y as a function of x), but it's not a graph of collisions as a function of buckets, either, because reading it that way implies that a very small number of buckets produces a small number of collisions, which is obviously false with a hundred million inputs being distributed over ten or less buckets.

It looks like a graph of the moral equivalent of 1=1, by numeric methods. What am I supposed to see there?