Fundamentals

Endowment Effect: Why We Value What We Already Own More

By Daniel Sardá · Published on October 14, 2026

6 min read1,257 words

Owning a good can raise the price we require to part with it. The endowment effect helps explain that gap, although it does not always appear and has no single cause.

Imagine receiving a mug as a gift. Before you owned it, you might not have paid ten dollars for it. Minutes later, when someone offers to buy it, ten dollars may no longer seem enough. The mug has not changed. Neither has the market. What has changed is your relationship to the object: it is now yours.

Behavioral economics calls this tendency the endowment effect: people may value a good more once they possess it than they did before acquiring it. This does not mean that everyone overvalues everything they own, or that keeping an item is always a mistake. It describes a pattern that can arise in certain decisions and depends on the good, the context, and how the exchange is framed.

When selling feels different from buying

A sale involves two similar but distinct questions. One is how much a person would pay to obtain a good. The other is the minimum amount they would accept to give up a good they already hold.

Economic research refers to willingness to pay (WTP) and willingness to accept (WTA). If someone would pay no more than $8 for a mug, but after receiving it requires at least $15 to sell it, there is a gap between the two valuations.

That gap is consistent with the endowment effect, but it does not establish it by itself. A seller and buyer may have different information, face different costs, or understand the situation differently. It also matters whether they understand the exchange mechanism and have experience bargaining.

Key idea: The endowment effect is not in the object. It lies in how possession can change the standpoint from which we assess keeping or giving it up.

Reference points and loss

The traditional explanation begins with a reference point. Before acquiring the mug, not having it is the normal state. Once it has been received, keeping it becomes the reference point, and surrendering it may feel like a loss.

This connects the endowment effect to loss aversion: in some decisions, giving something up weighs more heavily than gaining a comparable benefit. Still, the two concepts should not be treated as synonyms. Loss aversion is one possible explanation for the effect; it does not show that it is the only cause.

The literature has also considered other mechanisms. These include the prices people use as reference points, biased processing of the qualities of what is theirs, psychological ownership, and even strategic motives when setting a price. Emotional attachment can intensify a valuation, but it does not define the endowment effect. In the classic experiments, it was enough to assign an ordinary object at random; participants did not need to have kept it for years or connected it to personal memories.

What the mug experiment showed

One of the best-known studies was published in 1990 by Daniel Kahneman, Jack Knetsch, and Richard Thaler. In one experimental market, some participants received mugs and could sell them, while others could buy them. The initial allocation helped separate the act of receiving a good from pre-existing preferences for owning it.

In the first version of that market, the researchers predicted 11 trades per round but observed between one and four. In addition, sellers’ median valuations were more than twice those of buyers. The authors interpreted the scarcity of trades as evidence that the initial endowment could change valuation and prevent exchanges that would otherwise have taken place.

The finding was influential because it showed a shift even with a simple good that had just been assigned. It also challenged the idea that the initial distribution of goods is always irrelevant to later exchange.

Yet receiving a mug in a laboratory does not exhaust the legal or social meaning of property. Possession and property are not the same thing: the experiment changes who holds the object and who must give it up in order to trade; it does not provide a complete theory of property rights.

Useful distinction: A difference between WTA and WTP is evidence to interpret, not a verdict. Not every price gap automatically reveals a psychological bias.

Why the effect is not a universal law

Later evidence required a more qualified account. In 2005, Charles Plott and Kathryn Zeiler ran experiments with mugs and lotteries that incorporated anonymity, detailed training, and mechanisms intended to align incentives. Under those conditions, they did not find a gap between willingness to accept and willingness to pay.

Their work did not prove that the endowment effect does not exist. It did show that experimental procedure, understanding of the task, and incentives can change the result. A 2015 review by Carey Morewedge and Colleen Giblin likewise presents a plural picture: the kind of good, the context, and several psychological or strategic mechanisms can all matter.

It would therefore be excessive to conclude that people are “irrational” whenever they reject an offer. An object may have a special use for its owner, be hard to replace, or involve search and transaction costs. Even physically identical goods may occupy different places in different people’s plans. Value is subjective, while a market price emerges only when the parties’ valuations make an agreement possible.

How to notice it in an everyday decision

The concept is useful as a self-check. Suppose you want to sell a bicycle you barely use. You ask $500, even though you would not buy an equivalent bicycle for that amount today. The difference may reflect its condition, the costs of replacing it, or a legitimate personal connection. But it may also indicate that mere possession is influencing your reservation price.

To examine the decision without denying your autonomy, ask yourself three questions:

• If I did not own this good, how much would I pay for an equivalent one today?
• What real costs would I face in selling it and replacing it?
• Am I valuing its future usefulness, or defending the price because it is already mine?

Comparing offers, looking up the prices of similar goods, or using an intermediary can provide information. None of these tools decides for the owner. They simply make the distance between that person’s valuation and those of potential buyers more visible.

For better decisions: Revisiting a reservation price does not oblige anyone to sell. It helps distinguish what comes from usefulness, costs, and attachment from what may come from the mere fact of ownership.

What it teaches about exchange

The endowment effect does not invalidate voluntary exchange or imply that there is a “correct” price to impose on the parties. Instead, it reminds us that preferences are formed in concrete circumstances. Initial allocation, information, and the way a choice is presented can alter what each person is willing to offer or accept.

The practical lesson is modest but valuable: before rejecting an offer or setting a price, it can help to look at the good as though it were not yet ours. If the valuation remains the same, there may be good reasons to keep it. If it changes sharply, we have identified an influence worth considering. The decision remains one’s own, but it has been examined more carefully.

Sources

• Richard Thaler, “Toward a Positive Theory of Consumer Choice” (1980).
• Daniel Kahneman, Jack Knetsch, and Richard Thaler, “Experimental Tests of the Endowment Effect and the Coase Theorem” (1990).
• Charles Plott and Kathryn Zeiler, “The Willingness to Pay–Willingness to Accept Gap…” (2005).
• Carey Morewedge and Colleen Giblin, “Explanations of the Endowment Effect: An Integrative Review” (2015).