Where the words come from
What an externality is, pollution as a negative externality, social costs as private plus external costs, the higher price and lower quantity once external costs are counted, over-production as a market failure, deadweight loss, and the refrigerator figures — Principles of Economics 2e, OpenStax, licensed CC BY 4.0. https://openstax.org/books/principles-economics-2e/pages/12-1-the-economics-of-pollution. Changes: The curves S private and S social relabelled MPC and MSC as UK specifications name them; the refrigerator figures (a price of 650 and 45,000 fridges, an external cost of 100, and 700 and 40,000 once it is counted) converted from dollars to pounds, and the welfare-loss area computed by us from the straight-line table; the cement-works example invented; British spelling; the external cost card's definition is ours, built on 2e's "external costs of pollution that pass on to society" and framed as the gap between MSC and MPC so that it does not restate the definition box; the Pigouvian tax sentence in the first movement and the recap, the consumption-side externality in the set's intro, and the consumption-or-production check are ours (29 September).
The question and the page layout are our own.