A windfall gain is an unexpected increase in a person's or company's income or wealth that did not come from planned effort or investment. Common examples include lottery and prize winnings, an unexpected inheritance, a legal settlement, a sudden rise in the price of an asset someone already owns, and one-off government payments such as pandemic stimulus cheques. For companies, windfalls typically arise when an outside event, such as a war or supply shock, drives up the price of what they sell without any change in their own costs.
The term comes from fruit blown off trees by the wind, which the landowner could gather freely. In economics, windfalls are studied because they offer a clean test of how people respond to extra money, and because large corporate windfalls often prompt calls for a windfall tax. A windfall gain is the opposite of an unexpected loss and is related to, but narrower than, a capital gain, which can be planned or expected.
A windfall gain in plain terms
Suppose you find a forgotten $50 note in a winter coat. You did nothing to earn it this month, and you were not counting on it. Many people treat that money differently from their salary: they might spend it on a treat rather than paying a bill, even though a dollar is a dollar.
A windfall gain is that found note on any scale, from a small tax refund to a lottery jackpot or a surge in the value of a house. Economists study what people do with such surprises because it shows how they really make spending and saving decisions.
Windfalls in economic theory
Standard theories of consumption, such as the permanent income hypothesis and the life-cycle hypothesis, predict that a rational person spreads a one-off windfall over the rest of their life. A $10,000 gain would raise yearly spending only a little, with most of it saved at first. The share of extra income that is spent is called the marginal propensity to consume.
Behavioral economics offers a different view. Richard Thaler's idea of "mental accounting" holds that people sort money into separate mental accounts, so a windfall may be treated as "play money" and spent more freely than regular pay, or alternatively saved in full if it is large. Research on tax refunds and stimulus payments in the United States has found that households often spend a noticeable share within months, more than simple theory predicts, especially those with little cash on hand. The same logic underlies the wealth effect, where rising house or share prices lift consumer spending even though no money changes hands.
Evidence from lottery studies
Lotteries are a natural experiment, because winners are chosen at random. A 2001 study by Guido Imbens, Donald Rubin and Bruce Sacerdote of Massachusetts lottery winners who received yearly prize payments found that winners reduced their labor earnings modestly, by roughly 11 cents for each extra dollar of yearly prize income. Studies of Swedish lottery winners by David Cesarini and co-authors found similar small reductions in work, little effect on the health of adult winners, and limited effects on their children's outcomes. Popular stories of winners going broke exist, but systematic studies show more varied results. This research informs debates on universal basic income and the negative income tax, because it shows how people's willingness to supply labor changes when they receive money unrelated to work.
Corporate and national windfalls
Firms receive windfalls when market prices jump for reasons outside their control. Oil and gas producers in 2022, when energy prices surged after Russia's full-scale invasion of Ukraine, and some banks when interest rates rose quickly, are recent examples. Governments may respond with windfall taxes, as the United Kingdom did with its Energy Profits Levy from 2022 and the European Union with a temporary solidarity contribution on fossil fuel firms. Economists generally see a one-off tax on a truly unexpected gain as having little effect on behaviour, because it cannot change decisions already made, but warn that repeated windfall taxes can reduce future investment. Countries that discover oil or other resources face a national version of the same issue, managed through sovereign wealth funds and linked to the resource curse. The unearned element of such gains is close to what economists call economic rent.
Tax treatment
Tax rules for personal windfalls vary. In the United States, gambling and lottery winnings and most prizes are taxable income, and large wins are subject to federal withholding tax. In the United Kingdom, National Lottery prizes are not subject to income tax or capital gains tax, though the money becomes part of the winner's estate for inheritance tax. Inheritances are taxed through estate or inheritance taxes in some countries and not at all in others, and gains on assets are generally taxed under capital gains tax rules when sold.