An extra 290,000 pounds a year for lighting and cleaning because smog darkens and pollutes everything: with this cost estimate for the industrial city of Manchester, the English economist Arthur Cecil Pigou once founded the theory of environmental taxation. In the classic "The Economics of Welfare," the first edition of which was published as early as 1920, he proved that by allowing such 'externalities' to flow into product prices, the state can maximize welfare. In 2020, exactly 100 years later, the political implementation of Pigou's insight has gained strength, important objections are being invalidated, and carbon pricing appears more efficient than regulations and bans according to a study by the Potsdam Institute for Climate Impact Research (PIK) and the Mercator Research Institute on Global Commons and Climate Change (MCC). The study was published in the renowned journal International Tax and Public Finance.