Endowment effect

The endowment effect is the tendency of individuals to value an object more highly once they own it than they would if they did not — a cognitive asymmetry that cannot be explained by transaction costs, risk aversion, or standard preference theory. It was first demonstrated experimentally by Richard Thaler in 1980, and it is now understood as a direct consequence of loss aversion: to part with an owned object is to experience a loss, while to acquire the same object is merely to experience a gain, and losses are weighted more heavily.

The effect is robust across cultures and commodities, from coffee mugs to financial assets, and it violates the standard economic assumption that willingness to pay (WTP) and willingness to accept (WTA) should converge for the same good. The disparity between WTP and WTA is not a market friction; it is a cognitive law that restructures how markets function when agents are attached to their current endowments. In institutional design, the endowment effect explains why property rights allocations are sticky — once assigned, they are treated as reference points that resist reallocation even when efficiency gains are available.