Jevons Paradox, explained.
Jevons's Paradox describes a case where greater resource efficiency encourages enough additional use that total resource consumption rises instead of falling.
Why it happens
Efficiency reduces resource use per unit of service, but may make that service cheaper or more attractive. Total consumption multiplies resource use per unit by the number of units used. A rebound can offset some savings; backfire occurs only when it offsets more than all of them.
Unit savings and behavioral response must be considered together.
Read the result
Separate efficiency gains from the change in usage. Compare total resource use with the original baseline rather than looking only at consumption per task.
A worked example
Cheaper computation, more computation
A service initially runs 100 tasks using one energy unit each.
An improvement halves energy per task. If use rises to 300 tasks, consumption becomes 150 units.
Each task is more efficient, yet total consumption rises. If usage stayed at 100 tasks, consumption would fall to 50.
OPTIONAL DEEPER DETAILGo deeper: inside the model
Inside this model
Baseline use is 100. Each task consumes 1−e times as much resource, while task count grows by 1+rebound×e. Total use is 100(1−e)(1+rebound×e); rebound is a chosen response coefficient.
Where this idea is useful
A practical use
Cheaper travel per mile may encourage more miles traveled.
A common misconception
“Every efficiency improvement increases consumption.”
Rebound varies. It can be small, partial, or large enough to cause backfire; efficiency alone does not determine the total.
What this explanation leaves out
- Rebound strength is a scenario assumption, not an estimate of any specific technology or policy.
Is partial rebound the same as the paradox?
No. Partial rebound reduces the expected savings while still leaving total use lower. The stronger paradox involves total use exceeding the original baseline.
What happens to the number of tasks when each task becomes cheaper?
Associated thinkers
Further reading
Explore the original research or the teaching reference behind this experiment.