
David Simon, creator of The Wire, takes a crack at it:
Thirteen percent. The last time I paid taxes at that rate, I believe I might still have been in college…. I can’t get over the absurdity of this moment, honestly: Hey, I never paid less than thirteen percent. I swear. And no, you can’t examine my tax returns in any more detail. But I promise you all, my fellow American citizens, I never once slipped to single digits. I’m just not that kind of guy.

13% just makes him a bad tipper.