Jordi Brandts

Competition with forward contracts: a laboratory analysis motivated by electricity market design

We use experiments to study the efficiency effects for a market as a whole of adding the possibility of forward contracting to a pre-existing spot market. We deal separately with the cases where spot market competition is in quantities and where it is in supply functions. In both cases we compare the effect of adding a contract market with the introduction of an additional competitor, changing the market structure from a triopoly to a quadropoly. We find that, as theory suggests, for both types of competition the introduction of a forward market significantly lowers prices. The combination of supply function competition with a forward market leads to high efficiency levels.

Adjustment patterns and equilibrium selection in experimental signaling games

This paper examines the relation between adjustment patterns and equilibrium selection in laboratory experiments with two types of simple signaling games. One type of game has two Nash equilibria, of which only one is sequential. The other type has two sequential equilibria, only one of them satisfying equilibrium dominance. For each type of game, the results show that variations in the payoff structure, which do not change the equilibrium configuration, generate different adjustment patterns. As a consequence, the less refined equilibrium is more frequently observed for some payoff structures, while the more refined equilibrium is more frequently observed in others.

24. Pricing in Bertrand competition with increasing marginal costs

Bertrand competition under decreasing returns involves a wide interval of pure strategy Nash equilibrium prices. We first present results of experiments in which two, three and four identical firms repeatedly interact in this environment. More firms lead to lower average prices. However, prices remain substantially above the Walrasian level. With more than two firms the predominant market price is 24, a price not predicted by conventional equilibrium theories. This phenomenon can be captured by a simple imitation model and by a focal point explanation. For the long run, the model predicts that prices converge to the Walrasian outcome. We then use data from three new treatments to properly test the influence of imitation and focality. We find that both forces are present, but that imitation dominates in large markets with a long interaction.

An exploration of reputation formation in experimental games

This paper presents results from experiments with finitely repeated games with complete and incomplete information. We use two treatment variables: the number of rounds the game is played and the value of the probability that reflects the presence of incomplete information.

Limitations of dominance and forward induction: Experimental evidence

Abstract Forward induction implied that forgoing a sure ‘outside option’ can alter after subsequent beliefs and behavior. Our laboratory results do not support forward induction, except in a very simple game where it is equivalent to the elimination of dominated strategies.

Collusion and Fights in an Experiment with Price-Setting Firms and Production in Advance ∗

We present results from 50-round market experiments in which firms decide repeatedly both on price and quantity of a completely perishable good. Each firm has capacity to serve the whole market. The stage game does not have an equilibrium in pure strategies. We run experiments for markets with two and three identical firms. Firms tend to cooperate to avoid fights, but when they fight bankruptcies are rather frequent. On average, pricing behavior is closer to that for pure quantity than for pure price competition and price and efficiency levels are higher for two than for three firms. Consumer surplus increases with the number of firms, but unsold production leads to higher efficiency losses with more firms. Over time prices tend to the highest possible one for markets both with two and three firms.

Collusion in Growing and Shrinking Markets: Empirical Evidence from Experimental Duopolies

We study collusive behaviour in experimental duopolies that compete in prices under dynamic demand conditions. In one treatment the demand grows at a constant rate. In the other treatment the demand declines at another constant rate. The rates are chosen so that the evolution of the demand in one case is just the reverse in time than the one for the other case. We use a box-design demand function so that there are no issues of finding and co-ordinating on the collusive price. Contrary to game-theoretic reasoning, our results show that collusion is significantly larger when the demand shrinks than when it grows. We conjecture that the prospect of rapidly declining profit opportunities exerts a disciplining effect on firms that facilitates collusion and discourages deviation.

I Want You! An Experiment Studying the Selection Effect when Assigning Distributive Power

We study whether selection affects motivation. In our experiment subjects first answer a personality questionnaire. They then play a 3-person game. One of the three players decides between an outside option assigning him a positive amount, but leaving the two others empty-handed and allowing one of the other two players to distribute a pie. Treatments differ in the procedure by which distributive power is assigned: to a randomly determined or to a knowingly selected partner. Before making her decision the selecting player could consult the personality questionnaire of the other two players. Results show that knowingly selected players keep less for themselves than randomly selected ones and reward the selecting player more generously.

The impact of advice on women's and men's selection into competition

We conduct a laboratory experiment to study how advice by a more experienced and better-informed person affects an individuals entry into a real-effort tournament and the gender gap. Our experiment is motivated by the concerns raised by approaching the gender gap through affirmative action policies. Overall, advice improves the entry decision of subjects, in that forgone earnings due to wrong entry decisions go significantly down. The improvements are mainly driven by increased entry of strong-performing women, who also become more confident, and reduced entry of weak-performing men. We find that the overall gender gap persists even though it disappears among low and strong performers. The persistence is due to an emerging gender gap among intermediate performers driven by women (men) following more the advice to stay out of (enter) the tournament in this performance group. This paper was accepted by Uri Gneezy, behavioral economics.

Pivotal Suppliers and Market Power in Experimental Supply Function Competition

We use experiments to study market power with supply function competition, akin to the competition in electricity markets. Our treatments vary the distribution of demand levels as well as the amount and symmetry of the allocation of production capacity between different suppliers. We relate our results to a descriptive power index and to the predictions of two models: a supply function equilibrium (SFE) model and a multi-unit auction (MUA) model. Observed behaviour is consistent with the equilibria of the unrestricted SFE model and inconsistent with the unique equilibria of two refinements of the SFE model and of the MUA model.