Jevons paradox and productivity: where the time you save actually goes

In 1865 William Stanley Jevons published The Coal Question, a book arguing that Britain’s coal would run out. In its seventh chapter he took on the hopeful view that more efficient engines would stretch the supply, and wrote, in a line still widely quoted: “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.”

His evidence was the steam engine. James Watt’s design wasted less coal per unit of work, which made steam power cheap enough to spread into more industries, and total coal burned went up.

That is the Jevons paradox: an efficiency gain can raise total consumption when the cheaper resource finds new uses. Whether it applies to time is a separate question, and this post treats it as an analogy only. Nobody has shown that saved minutes behave like saved coal. The analogy is still useful, because the pattern it predicts is familiar: a tool gives back an hour, and by evening the hour is gone with nothing to show.

Does the Jevons paradox actually hold?

Less often than the slogan suggests. Economists call the general effect “rebound”: some of an efficiency saving is spent again. Sorrell, Dimitropoulos and Sommerville (Energy Policy, 2009) reviewed the evidence and concluded that the direct rebound for household energy services in OECD countries is generally below 30 percent, meaning net savings survive. Gillingham, Kotchen, Rapson and Wagner argued in Nature in 2013 that the rebound effect is “overplayed” as a reason to doubt efficiency policy. A full Jevons outcome, where use rises overall, needs demand that stretches easily, and Jevons was writing about coal as the engine of a whole industrial economy.

So the careful claim is narrow: efficiency does not guarantee savings, and the gap between what was saved and what was kept depends on where the spare capacity goes.

How is this different from Parkinson’s law?

Parkinson’s law says a task stretches to fill the time allowed for it. Jevons is about something else: a tool shrinks one task, and the recovered time is spent on other tasks, often more of them. Parkinson’s postcard takes all day. Jevons’s inbox takes ten minutes, and you answer twice as many emails. Both leave the day full, but they call for different fixes, one a tighter edge on the task and the other a decision about the freed time.

What does a 27-minute dividend look like?

Take a morning, as an illustration with made-up round numbers. An alarm set for 6:30, three presses of a snooze that has run nine minutes for decades (where the nine comes from), and you are up at 6:57. Three times nine is 27. Skip the presses and the 27 minutes are yours, five days a week making 135, a bit over two hours.

Those minutes, though, are not all lost to the snooze. Per the case that one snooze is probably fine, a single press may cost very little, so treat 27 as the upper end of the story. And if you do get them back, nothing says they will survive. They are the same fuel Jevons described, cheaper and open to any use, and the first thing to claim them is usually a screen. Journalist Brigid Schulte’s time confetti names what a free fragment turns into when nothing was assigned to it.

What should saved time be for?

Decide before you save it. Call it a time dividend: the minutes an efficiency gain returns, with a purpose chosen in advance and attached to a goal you already have. Twenty minutes of the thing you keep not starting is a better use than any amount of general freedom. Put it at the front of the block, since minutes at the back are the ones new tasks absorb.

The morning is the easiest place to try this, because the gain is a clean number and the hour has few competitors. DontSnooze is one way to make the number real: when the alarm goes off you have 30 seconds to film yourself up, or a random photo from your camera roll goes to your friends, so the 27 minutes are not hypothetical on the first day. It does nothing about what you do with them. A person who films the video, sits on the edge of the bed and opens a feed has converted the dividend into coal.

Settings can help too: iOS 26 lets you pick a snooze length (what to set it to), which changes the arithmetic from 27 to something smaller, but not what happens to the minutes once they exist.