The endowment effect is the tendency for people to value something more highly simply because they own it. In experiments, owners usually ask for noticeably more money to give up an item than non-owners are willing to pay to get the same item. The gap between the two prices, "willingness to accept" (WTA) and "willingness to pay" (WTP), is how economists measure the effect.
The economist Richard Thaler named the effect in a 1980 paper on consumer choice, and it became one of the best-known results in behavioral economics. It is usually explained by loss aversion: giving up an owned item feels like a loss, while buying it feels like a gain, and losses weigh more. It matters for trade, law and policy because standard theory, including the Coase theorem, often assumes that who owns something first does not change where it ends up. Thaler received the Nobel Memorial Prize in Economic Sciences in 2017, partly for this line of research.
The endowment effect in plain terms
Imagine clearing out a cupboard before moving house. An old jacket you have not worn in years suddenly feels hard to part with, and if a friend offered to buy it you might name a price far above what you would ever pay for it in a shop. Nothing about the jacket has changed; what changed is that it is yours.
The same thing happens with houses, cars, concert tickets and even shares. Sellers tend to think their item is worth more than buyers do, partly because they remember what it means to them and partly because handing it over feels like losing something. That gap can stop deals from happening even when both sides would be better off trading.
Classic experiments
The most cited tests were published by Daniel Kahneman, Jack Knetsch and Richard Thaler in the Journal of Political Economy in 1990. Students in a classroom were randomly given a coffee mug or nothing. Owners were then asked the lowest price at which they would sell; non-owners were asked the highest price they would pay. Because the mugs were handed out at random, standard theory predicts that about half should change hands. In practice far fewer trades took place, and sellers' typical asking prices were roughly twice buyers' offers.
Earlier, Knetsch had given some participants mugs and others chocolate bars, then offered everyone a chance to swap. Most people in both groups kept what they had been given, even though the initial allocation was random. Later reviews of dozens of studies found WTA/WTP ratios well above 1 on average, with the largest gaps for goods that have no close market substitute, such as environmental quality or health and safety.
The ratio is a simple way to express the size of the effect:
Here WTA is the minimum an owner will accept to sell, and WTP is the maximum a non-owner will pay. If owners of a concert ticket want $120 and non-owners will pay at most $60, the ratio is . Standard theory predicts a ratio close to 1 for ordinary goods whose cost is small relative to the buyer's income.
Where the endowment effect matters
- Housing markets. Owners often anchor on what they paid or what they feel the home is worth, which can widen gaps between asking and offer prices and slow sales after prices fall.
- Investing. Holding on to inherited shares or a long-held position can reflect attachment rather than analysis, working against diversification and contributing to the disposition effect.
- Law and property rights. When courts or legislators assign property rights, the endowment effect suggests the initial allocation can stick, because the holder values the right more than others would pay for it. This weakens one assumption of the Coase theorem.
- Policy and valuation. In cost-benefit analysis, whether a policy is valued by WTA or WTP can change the answer substantially, which matters for environmental damages and compensation.
- Marketing. Free trials, test drives and "keep it for 30 days" offers rely partly on customers feeling ownership before they have paid.
Explanations and criticism
Loss aversion is the most common explanation, but not the only one. Some researchers point to psychological ownership: people value things associated with themselves. Others stress transaction costs, uncertainty about the item's quality (sellers know it, buyers do not, which is a form of asymmetric information), or strategic behavior: in a negotiation, asking high and offering low is sensible.
The effect's strength has been challenged. In 2005 Charles Plott and Kathryn Zeiler reported that when experiments carefully trained participants and removed possible misunderstandings, the gap between WTA and WTP for mugs largely disappeared; later work debated whether their design removed the effect or simply changed the reference point. John List found in studies of sports-card and collector markets in the early 2000s that experienced traders showed little endowment effect, suggesting market experience reduces it. Supporters reply that most consumers are not professional traders, so the effect still matters in everyday markets.
From a policy view, the endowment effect is one reason defaults matter: whatever people start with tends to stay put. It is related to status-quo bias, to the framing effect and to bounded rationality. It also shows why the distinction between sunk cost and current value is psychologically hard: what someone already holds feels different from what they could buy. Standard models, such as those in neoclassical economics, can absorb the effect with reference-dependent preferences, but the size of the gap remains an empirical question.
In financial markets the endowment effect may reduce trading volume and liquidity relative to models with perfectly rational traders, and it is one input into wider debates about the efficient market hypothesis. Its relationship with risk aversion is indirect: a person can be risk-neutral about bets and still reluctant to part with a mug.