I always get unreasonably pissed off when people call this the Dunning-Kruger effect. The actual Dunning-Kruger effect is the discrepancy between a person's actual and perceived competence, and it has nothing to do with knowledge, wisdom. Those are closely connected things, but they're not the same.
It's very similar in my mind. Though, the phenomenon applies to knowledge, too. As the area of your knowledge grows, so too does the perimeter of your ignorance.
...I'm not sure if I didn't word myself well enough or if you did some mental leap I don't get, but I don't see how your reply is related to what I wrote. Though, I think the most important thing in regards to this curve and actual Dunning-Kruger effect is that the effect examines a number of people, while this graph describes a single person.
The thing is, the Dunning-Kruger effect does not measure, ability, knowledge, competence, experience, or whatever, by itself. It compares perceived competence with actual competence, but without relation to how it changes over the process of learning, which is the essence of that graph.