In The Coal Question (1865), William Stanley Jevons argued that improving energy efficiency increases rather than decreases total energy use — the effect now called the Jevons paradox

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In The Coal Question (1865) the economist William Stanley Jevons (1835–1882) argued that "improving energy efficiency typically reduced energy costs and thereby increased rather than decreased energy use, an effect now known as the Jevons paradox." His case study was the steam engine: as James Watt's improvements made coal-fired engines far more efficient per unit of work, the falling cost of that work expanded the range of profitable uses, and Britain burned more coal in total, not less. The mechanism is a rebound effect in which efficiency gains lower the effective price of an energy service and thereby raise demand for it — and when the rebound exceeds 100%, net consumption rises.

The claim is one strand of Jevons's unusually wide output — he also co-launched the marginal revolution in economics with his 1871 Theory of Political Economy — but it is the strand with the longest reach. It gives the vault's economics-of-computing cluster a nineteenth-century antecedent, alongside the hydraulic economic models the vault already holds (claim-phillips-moniac-hydraulic-economic-computer-1949, claim-hydraulic-analog-computers-independently-invented-economics-engineering). More importantly, the same 1865 argument is now invoked directly in the debate over AI's energy appetite — see claim-jevons-paradox-invoked-in-ai-energy-debate-luccioni-2025 — making Jevons a rare cross-century bridge, developed in observation-jevons-double-bridge-victorian-logic-machine-to-ai-energy.

Revisit 2026-09-12 — the primary read, date and wording confirmed

A cross-model audit read The Coal Question itself: the Internet Archive's Google Books scan of the 1865 Macmillan first edition (extract_pdf, 366 pp., TLS verified, sha256 2cf75cfd528be06a0fa8e4b242c6456451c3122700f083cd1cde4a1fc95e1f90). The title page carries "London and Cambridge, Macmillan and Co. 1865." The paradox is stated in Chapter VI, "Of the Economy of Fuel," in Jevons's own words on p. 103: "It is wholly a confusion of ideas to suppose that the economical use of fuel is equivalent to a diminished consumption. The very contrary is the truth." He continues on p. 104: "It is the very economy of its use which leads to its extensive consumption. It has been so in the past, and it will be so in the future. Nor is it difficult to see how this paradox arises" — and gives the mechanism the body summarizes: a blast-furnace that uses less coal per ton of iron raises the trade's profits, attracts new capital, lowers the price of pig-iron, raises demand, and "eventually, the greater number of furnaces will more than make up for the diminished consumption of each" (pp. 104–105). The steam-engine case study is his too: the engine's history "is a history of successive steps of economy" from Savery through Newcomen and Smeaton to Watt, whose "two chief inventions of the condenser and the expansive mode of working are, simply, two modes of economising heat" (pp. 105–107). The body above is retained as written; the Tier-4 Wikipedia paraphrase it opens with is now provenance history, superseded as the best source by the primary quoted here. The routed question had been closed on 2026-08-07 by a mechanical quote-match against Wikipedia; this read is what actually answers it.