The most useful sentence in economics is seven words long.
People respond to incentives. Everything else is commentary.
It is not a complicated idea. If you tax something, you get less of it. If you subsidise something, you get more of it. Price something too high and people find alternatives. Price something too low and they consume too much. The predictions are reliable, the evidence is overwhelming, and governments ignore it every time.
Start with taxation.
Tax income and you get less income. People work less, retire earlier, move to lower-tax jurisdictions, or simply stop reporting. The elasticity is debatable but the direction is not. Every empirical study of top tax rates shows that beyond a certain point, revenue falls because behaviour changes.
Tax capital and capital leaves. A wealth tax sounds simple on paper. Identify the rich, assess their assets, collect a percentage each year. In practice, the rich move. They change residency, restructure holdings, shift assets into hard-to-value forms. The countries that have tried wealth taxes - France, Sweden, Germany, Denmark - have mostly abandoned them after discovering that the revenue was negligible and the capital flight was real.
Tax corporate profits and companies relocate their headquarters, shift their intellectual property, or simply invest elsewhere. Ireland’s 12.5% rate attracted the world’s technology companies and the tax base moved with them. France’s attempts to tax its way to prosperity drove entrepreneurs to London and Brussels. The pattern is so predictable that it should be taught in primary school, yet every generation of politicians rediscovers it with fresh indignation.
Now consider the consumer.
Conventional wisdom holds that consumers are irrational. They buy extended warranties. They do not switch their energy provider for a better deal. They take out high-interest loans instead of saving. The implication is that markets fail because people are stupid, and government must step in to protect them.
The conventional wisdom is wrong.
The person who buys the extended warranty is not stupid. They are buying peace of mind. They do not want to spend an hour on hold, disputing a repair, if the device breaks. The warranty is an insurance policy, and like any insurance policy, it costs more than the expected claim. That is the point. The premium covers the provider’s costs and profit. The buyer knows this and pays anyway because the alternative - the hassle, the uncertainty, the time - is worth more to them than the premium.
The person who does not switch energy providers is not lazy. The expected saving from switching is twenty or thirty pounds a year. The expected effort is an hour of paperwork, a phone call, and the risk of something going wrong with the switch. How much is your hour worth? If the answer is more than twenty pounds, staying put is the rational choice.
The person who rents instead of buying in an expensive city is often doing the arithmetic. A mortgage on a one-bedroom flat in London at current prices and interest rates costs more per month than renting the same flat. The difference goes to interest, not equity. Renting preserves liquidity and mobility. If the renter loses their job, and the next job is in another city, their time and cost of moving is much lower than having to sell a property. It looks like throwing money away until you calculate what the alternative actually costs.
These are not irrational choices. They are rational responses to the costs and risks of the alternatives - costs and risks that the policy designer has never had to face personally.
Uncover the hidden subsidy.
Government spending is a transfer of resources from one group to another. Every spending programme creates a constituency with a direct interest in its continuation. The recipients adapt their behaviour to the subsidy, then lobby to keep it. What began as a temporary intervention becomes a permanent entitlement.
The logic is simple. A subsidy for housing makes housing more expensive because the subsidy capitalises into prices. A subsidy for tuition makes tuition more expensive because universities capture the additional funding. A subsidy for solar panels inflates the price of installation because the subsidy is shared between the installer and the homeowner. The beneficiary is not the person the policy was designed to help, but whoever captures the subsidy first.
This is not an accident. It is what happens when you change the incentives. Subsidise something and the supply side adjusts to capture the subsidy. The intended recipient gets less and less over time. The provider gets more and more. The government, committed to the policy, increases the subsidy to compensate, and the cycle repeats.
Why this keeps happening.
If the predictions of incentive theory are so reliable, and the evidence is so clear, why does every government keep making the same mistakes?
Two reasons.
First, the time horizon of politics is shorter than the time horizon of economic adjustment. A politician needs to show results before the next election. The wealth tax sounds good at a press conference and the capital flight takes five years to materialise. By the time the damage is visible, someone else is in office. The incentive is to announce the popular policy and let the next government deal with the consequences.
Second, the costs of bad policy are diffuse and the benefits are concentrated. The group that benefits from a housing subsidy - developers, landlords, mortgage lenders - is small, organised, and politically active. The group that pays for it - taxpayers and future homebuyers - is large, disorganised, and barely aware the subsidy exists. The politics are straightforward: the concentrated group wins, the diffuse group loses, and the policy stays.
The point.
Incentives are not a detail. They are the main event. Every policy should be evaluated by one question: what behaviour does this reward? If the answer is something other than what the policy’s supporters claim, the policy will fail. It will fail predictably, expensively, and in the direction the incentives point.
People respond to incentives. They always have. They always will.
The rest is commentary.