Juan Dubra

DOES THE BETTER‐THAN‐AVERAGE EFFECT SHOW THAT PEOPLE ARE OVERCONFIDENT?: TWO EXPERIMENTS

We conduct two experimental tests of the claim that people are overconfident, using new tests of overplacement that are based on a formal Bayesian model. Our two experiments, on easy quizzes, find that people overplace themselves. More precisely, we find apparently overconfident data that cannot be accounted for by a rational population of expected utility maximizers who care only about money. The finding represents new evidence of overconfidence that is robust to the Bayesian critique offered by Benoit and Dubra (Jean-Pierre Benoit and Juan Dubra (2011). “Apparent Overconfidence.” Econometrica, 79, 1591–1625). We discuss possible limitations of our results.

Information revelation in auctions

Auction theory has emphasized the importance of private information to the profits of bidders. However, the theory has failed to consider the question of whether or not bidders will be able to keep their information private. We show that in a variety of contexts bidders will reveal all their information, even if this information revelation is (ex ante) detrimental to them. Similarly, a seller may reveal all her information even when this revelation lowers revenues. We also show that bidders may be harmed by private information.

Continuity and Completeness under Risk

Suppose some non-degenerate preferences R, with strict part P, over risky outcomes satisfy Independence. Then, when they satisfy any two of the following axioms, they satisfy the third. Herstein-Milnor: for all lotteries p,q,r, the set of as for which ap+(1-a)qRr is closed. Archimedean: for all p,q,r there exists a>0 such that if pPq, then ap+(1-a)rPq. Complete: for all p,q, either pRq or qRp.

DOES THE BETTER-THAN-AVERAGE EFFECT SHOW THAT PEOPLE ARE OVERCONFIDENT?: TWO EXPERIMENTS: Better-Than-Average and Overconfidence: Two Experiments

We conduct two experimental tests of the claim that people are overconfident, using new tests of overplacement that are based on a formal Bayesian model. Our two experiments, on easy quizzes, find that people overplace themselves. More precisely, we find apparently overconfident data that cannot be accounted for by a rational population of expected utility maximizers who care only about money. The finding represents new evidence of overconfidence that is robust to the Bayesian critique offered by Benoît and Dubra (2011). We discuss possible limitations of our results.

Information is not about measurability

We present a simple example where the use of σ-algebras as a model of information leads to a paradoxical conclusion: a decisionmaker prefers less information to more. We then explain that the problem arises because the use of σ-algebras as the informational content of a signal is inadequate. We provide a characterization of the different models of information in the literature in terms of Blackwell’s theorem.

A Theory of Rational Attitude Polarization

Numerous experiments have demonstrated the possibility of attitude polarization. For instance, Lord, Ross & Lepper (1979) partitioned subjects into two groups, according to whether or not they believed the death penalty had a deterrent effect, and presented them with a set of studies on the issue. Believers and skeptics both become more convinced of their initial views; that is, the population polarized. Many scholars have concluded that attitude polarization shows that people process information in a biased manner. We argue that not only is attitude polarization consistent with an unbiased evaluation of evidence, it is to be expected in many circumstances where it arises. At the same time, some experiments do not find polarization, under the conditions in which our theory predicts the absence of polarization.

Monotone Preferences Over Information

We consider preference relations over information that are monotone: more information is preferred to less. We prove that, if a preference relation on information about an uncountable set of states of nature is monotone, then it is not representable by a utility function.

Supermarket Entry and the Survival of Small Stores

We analyze the effect of supermarket entry on the exit of small stores in the food retailing sector in Montevideo between 1998 and 2007. We use detailed geographical information to identify the link between supermarket entry and the exit of nearby small stores. Entry of supermarkets using small- to medium-size formats creates a competitive threat for the existing small stores, decreasing their probability of survival. The result is robust to several model specifications and varying definitions of what constitutes a supermarket. The impact of supermarket entry is unequivocal for groceries, bakeries, fresh pasta shops, and butcher shops.

On the Problem of Prevention

Disasters are often precipitated by insufficient preventive care. We argue that there is a problem of prevention in that this lack of care often stems from agents’ rational calculations. Positive experiences lead agents to underestimate the risks of disasters; technological improvements and redundancies designed for safety induce agents to reduce their care. Although lower care increases the chances of an accident, the number of redundancies can be adjusted to offset this. However, the accident probability remains constant even as ostensible improvements in safety are made. Checklists can be used to decrease the number of accidents.

A correction to uniqueness in “Competitive Bidding and Proprietary Information”

Abstract In this note I show that there is a mistake in the proof of uniqueness in Engelbrecht-Wiggans, Milgrom and Weber’s seminal “Competitive Bidding and Proprietary Information” and provide a correct proof.