# The Coal Question

Source: https://dinand.com/reading-notes/the-coal-question/
Author: Dinand Tinholt

> William Stanley Jevons, 1865, on why a more efficient engine burns more coal.

![Technical engraving of a beam steam engine in elevation, with cylinder, beam, flywheel and detail drawings.](https://dinand.com/assets/reading-notes/the-coal-question.jpg)

*Watt’s double-acting steam engine, from his specification of 1782, engraved for John Robison’s System of Mechanical Philosophy (1822).Image: “Mr. Watt’s double steam engine”, engraving from John Robison’s System of Mechanical Philosophy, 1822. Library of Congress, Prints and Photographs Division. Public domain, via [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Steam_engine_-_Mr._Watt%27s_double_steam_engine_from_his_specification_of_1782_LCCN2006691752.jpg). Resized for this page.*

In 1865 William Stanley Jevons, twenty-nine years old, published The Coal Question. Britain was starting to worry about its coal running out, and plenty of people expected better engines to fix the problem. Jevons argued the opposite. Every improvement to the steam engine since James Watt had made coal cheaper to use, so industry found new jobs for it and total consumption rose.

Economists call this the rebound effect. When use grows past the savings, they call it the Jevons paradox.

## Cheaper tokens, more tokens

Running a language model at a given quality has become far cheaper since 2023. Spending on inference has gone up anyway, because cheap calls invite agents that make thousands of them where a person once asked one question.

Oversight follows the same arithmetic. In one of my simulations the cost of monitoring a portfolio of agents grew faster than the number of agents, with an exponent of about 1.47. You can play with the curve in the [monitoring cost explorer](https://dinand.com/experiments/monitoring-cost-explorer/). Cheaper agents mean more agents, and each one adds more review work than the one before.

Jevons got his own forecast wrong. He expected British growth to stall as coal grew scarce, and he never saw oil coming. The mechanism he described has held for a hundred and sixty years, through electricity and computing, and it is holding for inference.

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## A next room to enter.

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[Reading Notes · Reading note

### The Nature of the Firm

Ronald Coase asked in 1937 why firms exist at all. AI agents reopen his question.

](https://dinand.com/reading-notes/the-nature-of-the-firm/)[Reading Notes · Reading note

### The Dynamo and the Computer

Paul David, 1990, on why electricity took forty years to show up in the productivity numbers.

](https://dinand.com/reading-notes/the-dynamo-and-the-computer/)[Reading Notes · Reading note

### Seeing Like a State

James C. Scott on scientific forestry, and the work a dashboard leaves out.

](https://dinand.com/reading-notes/seeing-like-a-state/)

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