COLLUSION IN THE PRESENCE OF EXTERNALITIES*

I examine collusive bidder behavior in auctions with negative externalities and show that the optimal bidding scheme exhibits only partial rigidity. Because of externalities, a cartel not only has incentive to maximize gains from trade but also to minimize the probability of sales. I identify the tension between the two incentives and show that the more rigid the bidding scheme, the higher the possibility of sales. As the extent of externalities increases, the cartel finds it more important to keep a low probability of sales than to minimize payment to the seller. This results in a partially‐rigid optimal collusive bidding scheme.     

Post-cartel tacit collusion: Determinants,consequences, and prevention

We experimentally investigate the determinants of post-cartel tacit collusion (PCTC), the effects of PCTC on market outcomes, and potential policy measures aimed at its prevention. PCTC occurs robustly with or without fines or leniency and is determined both by collusive price hysteresis and learning about cartel partners’ characteristics and strategies. As a result, it is also strongly related to the preceding cartel success. PCTC generates a downward bias in the estimated cartel overcharges. This threatens the effectiveness of deterrence induced by private damage litigation and fines imposed on colluding firms based on the overcharge. This bias further increases with preceding cartel stability such that especially more stable sets of colluding firms may be deterred less when PCTC is present. Rematching colluding subjects with strangers within a session prevents PCTC. This indicates that barring colluding managers from their posts could help impede PCTC in the field.     

Competition,Innovation and the Use of Innovations

I examine the effect of competition on the production and use of innovations using evidence from a natural experiment of policy reform, the introduction of cartel legislation in the U.K. in the late 1950’s. I compare manufacturing industries which had been collusive and were therefore affected by the policy with those that had been competitive and were not affected. The intensification of competition following the abolition of cartels caused a short‐run decrease in innovations produced, but had no significant effect in the long run. In contrast, innovations used increased both in the short run and in the long run.     

Cartel Attributes and Cartel Performance: The Impact of Trade Associations

This paper employs a cartel policy experiment, the National Industrial Recovery Act of 1933, to examine whether industries that have trade associations in place prior to cartelization were better able to attain collusive outcomes than otherwise. Trade associations could potentially help industries better formulate effective cartel rules and could help with monitoring. We find that industries with trade associations were more successful in achieving collusion–proxied by either reductions in industry output or increases in industry prices–than those without. In fact, industries without trade associations were generally unable to successfully collude under the NIRA.     

Cartel pricing dynamics with cost variability and endogenous buyer detection

This paper characterizes collusive pricing patterns when buyers may detect the presence of a cartel. Buyers are assumed to become suspicious when observed prices are anomalous. We find that the cartel price path is comprised of two phases. During the transitional phase, price is generally rising and relatively unresponsive to cost shocks. During the stationary phase, price responds to cost but is much less sensitive than under non-collusion or simple monopoly; a low price variance may then be a collusive marker. Compared to when firms do not collude, cost shocks take a longer time to pass-through to price.     

Civil antitrust sanctions and cartel stability

A simple model is used to examine the effects of accumulating civil damage liability on the stability of collusive agreements. We demonstrate that all collusive agreements have a built-in upper bound wherein it is no longer profitable to continue collusive activity. A consequence of this upper bound is that the well known "final period problem" comes into play leading to cartel instability. A modification of the initial model demonstrates how a statute of limitations on antitrust actions can mitigate or eliminate the final period problem. Finally, we discuss how the statute of limitations works in practice.     

Identifying Participants in a Price-fixing Conspiracy: Output & Market Share Tests Reexamined

If there is a cartel agreement among a subset of firms in an industry, it should be predicted that all firms in that industry will increase prices. Nevertheless, industry prices alone should not indicate that a particular firm is guilty of that conspiracy. According to the output test and its market share variant – proposed by Blair and Romano – if the output or the market share of the firm that claims to be innocent in the collusive activity rises in response to the price increase, that firm's claim should be accepted as true. Using a collusive variant of the dominant firm model, this paper shows that these are not robust tests to reveal either innocence or guilt, and characterizes cases where they may pardon a guilty firm (Type I error) or indict an innocent firm (Type II error). This paper also shows that a market share test can not be used to prove a dominant firm's intent for predatory pricing.     

Collusion at the extensive margin

We augment the multi-market collusion model of Bernheim and Whinston (1990) by allowing for firm entry into, and exit from, individual markets. We show that this gives rise to a new mechanism by which a cartel can sustain a collusive agreement: Collusion at the extensive margin whereby firms collude by avoiding entry into each other's markets or territories. We characterise parameter values that sustain this type of collusion and identify the assumptions where this collusion is more likely to hold than its intensive margin counterpart. Specifically, it is demonstrated that where duopoly competition is fierce collusion at the extensive margin is always sustainable. Finally, we provide a theoretic foundation for the use of a “proportional response” enforcement mechanism.     

Flagging cartel participants with deep learning based on convolutional neural networks

Adding to the literature on the data-driven detection of bid-rigging cartels, we propose a novel approach based on deep learning (a subfield of artificial intelligence) that flags cartel participants based on their pairwise bidding interactions with other firms. More concisely, we combine a so-called convolutional neural network for image recognition with graphs that in a pairwise manner plot the normalized bids of some reference firm against the normalized bids of any other firms participating in the same tenders as the reference firm. Based on Japanese and Swiss procurement data, we construct such graphs for both collusive and competitive episodes (i.e when a bid-rigging cartel is or is not active) and we use a subset of graphs to train the neural network such that it learns distinguishing collusive from competitive bidding patterns. With the remaining graphs, we test the neural network’s out-of-sample performance in correctly classifying collusive and competitive bidding interactions. We obtain a very decent average accuracy of around 95% or slightly higher when either applying the method within Japanese, Swiss, or mixed data (in which Swiss and Japanese graphs are pooled). When using data from one country for training to test the trained model’s performance in the other country (i.e. transnationally), predictive performance decreases (likely due to institutional differences in procurement procedures across countries), but often remains satisfactorily high. All in all, the generally quite high accuracy of the convolutional neural network despite being trained in a rather small sample of a few 100 graphs points to a large potential of deep learning approaches for flagging and fighting bid-rigging cartels.     

Price-Matching Guarantees and Equilibrium Selection in a Homogenous Product Market: An Experimental Study

Price-matching guarantees have been alleged to sustain collusive prices in a homogenous product market. Theories in this literature also suggest that there exist multiple equilibria (i.e., a set of price equilibria between the competitive and the monopoly price) when all sellers adopt these guarantees in such a market. Theoretical prediction in this case fails to pin down the actual behavior of players a priori. This paper illustrates the essential role of controlled experiment in testing the collusive theory of price-matching guarantees and thereby shedding light on the embedded equilibrium selection problem. In particular, this paper studies two highly stylized market models, obtains testable predictions, and lays out the design of the controlled experiment. Results indicate that these guarantees facilitate collusion among sellers and thus solve the equilibrium selection problem considerably. I am grateful to Jim Cox, Martin Dufwenberg, Haimanti Bhattacharya, and the editor of this journal and the two referees for their suggestions. I thank seminar participants at the University of Arizona and North American Economic Science Association meeting at Tucson, 2003 for their helpful comments. A research grant from ESL, University of Arizona, for this project is gratefully acknowledged. I am solely responsible for any remaining errors and omissions.     

A Holy Alliance: Collusion in the Renaissance Europe Alum Market

On June 11, 1470, representatives of Pope Paul II and Ferdinand, King of Naples concluded a cartel agreement to restrict competition in the sale of alum. The agreement was one element of a broader plan to monopolize the sale of alum throughout Christendom. We discuss the background of the cartel agreement and analyze its terms (which include arrangements to facilitate detection of and reduce the profitability of defection) and the constraints that limited, but did not eliminate, Rome’s ability to extract economic profit from the European alum market.     

The impact of leniency and whistle-blowing programs on cartels

Antitrust authorities have set up leniency programs for cartel members that denounce their collusive agreements. These programs help prosecute participants and can thereby deter collusion. We compare the impact of reduced fines and positive rewards and argue that rewarding individuals, including firm employees, can deter collusion in a more effective way.We discuss possible adverse effects of whistle-blowing programs on firms' behavior, and particularly on turnover, incentives to innovate and cooperation. We also explore explanations for the puzzling fact that managers keep incriminating evidence and argue reward programs actually provide additional incentives for keeping such evidence.     

Auction cartels and the absence of efficient communication

This paper examines the feasibility of collusive mechanisms in single-unit auctions. A model is constructed with private and common value information asymmetry and continuous type space. We show that an incentive compatible bid coordination mechanism (BCM) does not exist if common value uncertainty is present. This result contradicts actual antitrust cases, where common effects or resale opportunities created uncertainty about valuations, but a price-fixing cartel was formed. We solve the puzzle by relaxing the assumption that all bidder types truthfully reveal their private information. The introduced Bayesian bid coordination mechanism (BBCM) exists if the main source of information asymmetry is private value. In that case, a designated ring member can signal high valuation and suppress competition. Our results demonstrate the rationale behind cartel mechanisms with pre-auction knockouts.     

Sales Promotion and Cooperative Retail Pricing Strategies

Supermarket retailers make strategic pricing decisions in a high-frequency, repeated game environment both in buying and selling fresh produce. In this context, there is some question as to whether a non-cooperative equilibrium can emerge that produces margins above the competitive level. Supermarket pricing results from tacitly collusive equilibria supported by trigger price strategies played in upstream markets. Upstream activities are, in turn, driven by periodic retail price promotions. This hypothesis is tested using a sample of fresh produce pricing data from 20 US supermarket chains. The results support the existence of tacitly collusive non-cooperative equilibria in upstream and downstream markets.     

Collusion between two-sided platforms

We study the price and welfare effects of collusion between two-sided platforms and show that they depend on whether collusion occurs on both sides or a single side of the market, and whether users single-home or multi-home. Our most striking result is that one-sided collusion leads to lower (resp. higher) prices on the collusive (resp. competitive) side if the cross-group externalities exerted on the collusive side are positive and sufficiently strong. One-sided collusion may, therefore, benefit the users on the collusive side and harm the users on the competitive side. Our findings have implications regarding cartel detection and damages actions.     

OUTPUT‐EXPANDING COLLUSION IN THE PRESENCE OF A COMPETITIVE FRINGE*

Following the structure of many commodity markets, we consider a few large firms and a competitive fringe of many small suppliers choosing quantities in an infinite‐horizon setting subject to demand shocks. We show that a collusive agreement among the large firms may not only bring an output contraction but also an output expansion (relative to the non‐collusive output level). The latter occurs during booms and is due to the strategic substitutability of quantities. We also find that the time at which maximal collusion is most difficult to sustain can be either at booms or recessions. The international copper cartel of 1935–39 is used to illustrate some of our results.     

Collusive Communication and Pricing Coordination in a Retail Gasoline Market

This paper studies how communication is used by a retail gasoline cartel in Australia to coordinate price increases, a role of communication in collusion not highlighted by Genesove and Mullin (Am Econ Rev 91(3): 379–398, 2001). A unique data set from the trial record allows for quantifying not only the pricing dynamics, but also the communication patterns. Both empirical and narrative evidence suggests the collusive communication and pricing behavior is well captured by the price cycle equilibrium of the Maskin and Tirole (Econometrica 56(3): 571–599, 1988) model.     

Mergers and coordinated effects

A merger is said to have coordinated effects if it results in more collusive outcomes. I review the theory of collusion, and the role played by communication in coordination. Mergers can affect the enforcement and participation constraints for a collusive agreement, and the selection from the equilibrium set of outcomes. I describe some recent empirical studies of the effects of mergers on collusion, and the underlying measurement issues associated with identifying the degree of coordination. I also discuss some recent cases in which coordinated effects were a concern, including both merger reviews and ex post investigations.     

Prosecution and Leniency Programs: The Role of Bluffing in Opening Investigations

This paper characterizes the optimal investigation and leniency policies when the Competition Authority is privately informed about the strength of a cartel case. I show that the Competition Authority can then exploit firms’ uncertainty about the risk of conviction to obtain confessions even when the case is weak. More generally, I show that offering full leniency allows the Competition Authority to open more successful investigations (what I refer to as the ‘activism effect’ of leniency), which overall raises both cartel desistance and cartel deterrence. Finally, I discuss the policy implications of the model.     

An oligopoly model of ocean liner shipping

In this paper I develop a simultaneous equations oligopoly model of the regulated international ocean liner shipping industry. The firms act as a cartel to determine price jointly and then set their own quality levels to maximize individual profits. The cartel does not attain monopoly profits, because each conference member myopically determines quality without regard for overall cartel profits. The results indicate that an increase in the number of firms in the cartel will increase both cartel price and quality level. An increase in price will also lead to an increase in quality level.I would like to thank Professors Alamarin Phillips, Robert Summers, and Bruce Allen for their helpful comments on earlier research for my dissertation in the Economics Department of the University of Pennsylvania on which this work is based. I am especially grateful to Professor Lawrence J. White for his encouragement and valuable suggestions at various stages of my work.