("willingness to accept") was approximately twice as high as the amount they were willing to pay to acquire the mug ("willingness to pay"). Other examples of the endowment effect include work by Ziv Carmon and Dan Ariely, who found that participants' hypothetical selling price (willingness to accept or WTA) for NCAA final four tournament tickets were 14 times higher than their hypothetical buying price (willingness to pay or WTP). Also, work by Hossain and List (Working Paper) discussed in the Economist in 2010, showed that workers worked harder to maintain ownership of a provisionally awarded bonus than they did for a bonus framed as a potential yet-to-be-awarded gain. In addition to these examples, the endowment effect has been observed using different goods in a wide range of different populations, including children, great apes, and new world monkeys. Background The endowment effect has been observed from ancient times: Psychologists first noted the difference between consumers' WTP and WTA as early as the 1960s. The term endowment effect however was first explicitly coined by the economist Richard Thaler in reference to the under-weighting of opportunity costs as well as the inertia introduced into a consumer's choice processes when goods included in their endowment become more highly valued than goods that are not. In the years that followed, extensive investigations into the endowment effect have been conducted producing a wealth of interesting empirical and theoretical findings. Theoretical explanations Loss aversion It was proposed by Kahneman and his colleagues that the endowment effect is, in part, due to the fact that once a person owns an item, forgoing it feels like a loss, and humans are loss-averse. They go on to suggest that the endowment effect, when considered as a facet of loss-aversion, would thus violate the Coase theorem, and was described as inconsistent with standard economic theory which asserts that a person's willingness to pay (WTP) for a good should be equal to their willingness to accept (WTA) compensation to be deprived of the good, a hypothesis which underlies consumer theory and indifference curves. However, these claims have been disputed and other researchers claim that psychological inertia, differences in reference prices relied on by buyers and sellers, and ownership (attribution of the item to self) and not loss aversion are the key to this phenomenon. Psychological inertia David Gal proposed a psychological inertia account of the endowment effect. In this account, sellers require