It was Pigou who in 1920 that came up with the concept of externalities, your not that old lol
Quite sure he came up in Economics 101 (micro) in my first year at uni, yes must of been because my first assignment was applying economic theory to a news paper article. I chose an article titled, "Increase in price of beer reduces sexually transmitted disease in". Sexually transmitted disease being the externalities and the increase in tax being the pigovian tax.
In that I explained that the extra cost impacted more on young adults who had less disposable income and where more inclined to have promiscuous sex compared to older adults
