Pigou not part of my economic study. He may have risen to fame, later than when I was a student. Mind you, I've always been aware of negative externalities, of course, and the disruption to equilibrium prices as a consequence of them not be recognised as a cost. Incorrect price signalling occurring as a consequence. Pretty sophisticated explanation given in Wikipedia of the type you'd expect to be on the curriculum of Economics, probably in final year of an undergrad. course. Did a double major in Economics, but never discovered Pigou. hmmmm.
