Curvas de indiferença comportamentais

A economia comportamental já aí anda há uns anos, mas até agora tem sido encarado mais como uma compilação dispersa de descobertas interessantes do que propriamente como uma parte integrante da teoria económica mainstream. Mas isso está a mudar e pode ler-se, no Vox, uma proposta para começar a incorporá-la na microeconomia: Sticky prices and beahavioural indifference curves.

According to conventional indifference curve diagrams, when deciding between two goods – say, food and clothing – it is as though we’ve never consumed them before. Thus, we are assumed to come to the problem in a pristine state, without indicating the amount of the goods in question we consumed in the prior period or are adapted to. However, this is contradictory, because if we have not consumed these items before, how are we supposed to know how much utility we should expect from them?

Hence, the customary indifference curve depends on the implicit assumption that choices along indifference curves are reversible. That is, if an individual owns x and is indifferent between keeping it and trading it for y, then when owning y the individual should be indifferent about trading it for x. If loss aversion is present, however, this reversibility will no longer hold (Knetsch 1989, Kahneman et al. 1991). Knetsch and Sinden (1984) were the first to point out that the standard assumption pertaining to the equivalence of losses and gains is contradicted by the experimental evidence.


In sum, behavioural indifference curves are relative to a reference point. The endowment effect implies that people are willing to give up an object only at a higher price than the price at which they are willing to buy it, i.e. it is psychologically more difficult to give up an object than to acquire it. This changes the shape and properties of the indifference map, which has far-reaching implications not only in classrooms, but also in applied areas such as the evaluation of welfare states and the stickiness of economic variables such as wages, prices, and interest rates (Knetsch et al. 2012). This salient issue ought no longer to be ignored, and needs a much wider research agenda than hitherto allotted to it at the margins of the discipline.

Even at this stage it is important to incorporate behavioural indifference curves into the curriculum and stop teaching outdated concepts. If you think that behavioural indifference curves would be too complicated for beginners then I would urge you not to teach the conventional ones until the students are ready for the current version, because one should not mislead students by teaching inappropriate concepts. If the straight-talking Nobel-prize-winning physicist Richard Feynman (1918–1988) were still with us, he would concur with this view. In his famous 1974 commencement address at the California Institute of Technology, he beseeched the graduating class to practice scientific integrity, utter honesty, and to lean over backwards so as not to fool themselves (and of course others) (Feynman 1985). I believe that the same is true for us – teachers of economics, it is time to start leaning over backwards and to stop teaching the standard indifference curves.



One comment on “Curvas de indiferença comportamentais

  1. “According to conventional indifference curve diagrams, when deciding between two goods – say, food and clothing – it is as though we’ve never consumed them before.”

    É? Quando aprendi, nunca vi ou ouvi nada que me desse essa ideia; é verdade que o modelo efetivamente ignora o efeito “se nunca usei, como sei que gosto”, mas isso tanto pode implicar que o modelo parte do principio que nunca os consumimos antes, como que parte do principio oposto – que conhecemos ambos os produtos.

    Mas este texto acaba até por, tangencialmente, abordar uma coisa que eu acho acerca da “economia comportamental”: muitos dos seus supostos exemplos de “comportamento não-racional” podem perfeitamente ser modelizados como “racionais” na melhor tradição neo-clásica; no caso especifico do “endowment effect”, é só assumir que há incerteza na utilidade esperada de consumir um dado produto, que essa incerteza diminui com o conhecimento do produto e que os agentes são avessos ao risco, e já está: um modelo neo-clássico puro e duro, com agentes perfeitamente racionais (ainda que com informação limitada).. e com “endowment effect”.


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