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lunes, 31 de enero de 2011

Lo último de Posner: sobre la incertidumbre

Con ocasión de recibir la medalla Coase.
Un acontecimiento es incierto cuando no podemos calcular con exactitud las probabilidades de que se produzca (si podemos, entonces se habla de riesgo). La incertidumbre
“impedes the use of cost–benefit analysis to identify optimal public or private investment, or other economic activities, since the costs or benefits (or both) of a proposed course of action are generally probabilistic rather than certain quantities. That is one reason economists do not like uncertainty and another is that it appears to inject irrationality into the study of the economic system
Los economistas se enfrenta al problema de la incertidumbre recurriendo a las “probabilidades subjetivas” (observando la conducta de los individuos podemos deducir qué probabilidad atribuyen a que se produzca un hecho. Por ejemplo, si la gente invierte mucho en medidas preventivas de los accidentes de tráfico es porque asignan una posibilidad significativa de que se produzca) . Pero si los particulares no saben cuál es la probabilidad de que un evento dañoso se produzca (por ejemplo, sufrir un accidente mortal de tráfico), no podemos deducir sus preferencias de la inversión que realizan en prevención del evento dañoso. O bien, atribuyendo una probabilidad arbitrariamente pequeña a la producción del evento, lo cual es muy poco útil cuando los daños que se esperan, si el acontecimiento se produce, son muy elevados (porque asignar una probabilidad un poco mayor o un poco menor modifica mucho la cuantía de los daños).
La influencia de la incertidumbre sobre la formación de burbujas
If stock prices are rising, no one knows how long the trend will continue; but the fact that many investors are buying (which is why prices are rising) is an indication that some investors, at least, think stocks a bargain and will continue buying, for a time anyway (others, though, may just be buying in the belief that other investors will keep buying). Thus, prices rise because prices are rising rather than because of changes in fundamentals of demand and supply.
Y la consecuencia
The point is not that economics needs psychology, viewed as the study of cognitive imperfections caused by emotions or brain limitations, for there is nothing irrational about momentum trading (and hence bubbles), … The point is simply that some well-accepted economic propositions, such as that stock prices just capitalize corporate earnings or that housing prices just capitalize rental values, have proved to be too simple.
La incertidumbre hace preferible seguir al rebaño aunque, subjetivamente, pensemos que el rebaño está equivocado. Porque seguir al rebaño, en esas circunstancias, es una conducta menos arriesgada.
Y, por último, cómo la incertidumbre hace que comportamientos aparentemente irracionales ¡por parte de empresas! no deban considerarse tales
… John Hicks famously said that “the best of all monopoly profits is a quiet life,” and this dictum has been derided by economic analysts of antitrust, including me, as ignoring the equivalence of out‐of‐pocket and opportunity costs. The monopolist who fails to run a tight ship is giving away money; and we know (this is another favorite dictum of economists) that no one fails to pick up a dollar bill that he sees lying on the sidewalk—that would be irrational because the time cost of picking up the dollar is bound to be less than a dollar. But organization economics and the Knight–Keynes concept of uncertainty can help us see that Hicks may have been right. If you are running a profitable business, or a profitable division of a business, and you are not certain—and how could you be certain?—that changing the operation of the business would make it more rather than less profitable, you will be rationally reluctant to change if, consistent with risk aversion, you weight losses more heavily than gains.
Por tanto, un monopolista, por definición, carece de presiones externas para ser más eficiente y, no introducirá cambios respecto de cuyos resultados no esté completamente seguro. Un argumento más para criticar la falta de realismo de los modelos que utilizan los economistas.

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