THE EVOLUTION OF CONCENTRATION. Henry Farrell, in commenting on mutually beneficial hitch-hiking (how else to describe the evolutions of locations where unaccompanied drivers can pick up passengers bound the same direction and qualify for a high-occupancy vehicle lane?) notes that "spontaneous order can involve persistent, and substantial distributional inequalities," linking to a study of the evolving agglomeration in an Italian manufacturing district. (I have had opportunity to read other work on this manufacturing district. The paper appears to merit a more careful reading than I have given it so far, perhaps it's something to read whilst proctoring.) Puzzle: is distributional inequality simply a phenomenon, or a troubling phenomenon? Start everybody with identical claims to goods. Now let one person become a singer that everyone else is willing to pay a small sum of money to hear at a concert. Instant, massive, mutually beneficial distributional inequality.