In the 1800s, coal was the sine qua non of economic development, essential for everything from heating to transport to manufacturing. In Britain, the country where the stuff first powered an industrial revolution, national leaders debated how concerned they should be about potentially depleting coal deposits. Some argued that supply would never be exhausted because improvements in steam engine designs would steadily reduce the amount of coal necessary to power a train, make a dress, or do anything else. Productivity gains would allow Britain’s coal resources to stretch further and further.
In his 1865 book The Coal Question, the economist William Stanley Jevons explained why he disagreed. Jevons drew from then-recent history to show that steam engines’ efficiency had led people to deploy more of them. “Burning coal became an economically viable thing to do, so demand exploded,” said Kenneth Gillingham, a professor of environmental and energy economics at Yale. “You have steam engines everywhere, and people are using them instead of water power. You actually use a lot more coal than you did initially.” Despite the improvements in steam engine design, Jevons argued, total coal use would continue to rise.
Today, the Jevons paradox describes a situation where greater efficiency in deploying a resource (such as water, gasoline, or electricity) causes demand for that resource to skyrocket — negating an expected decline in total usage. Electric lights are often cited as an example: people have responded to improved light bulb efficiency by installing so many more of them that there has been no decline in the total energy consumed by lighting. The Jevons paradox has become a bedrock principle of environmental economics, used to explain why efficiency improvements can backfire and cause the opposite outcome from what was intended.
Its lessons can also illuminate transportation. Consider the projects undertaken by highway agencies to alleviate roadway congestion. Public officials often justify them by noting (accurately) that gas-powered engines are less efficient and release more pollutants if they are stuck in gridlock instead of moving at a steady clip. For that reason, they argue, highway expansions or traffic technologies that mitigate traffic jams will also reduce emissions.