Arnold Polanski

Bilateral bargaining in networks

Abstract Each connected pair of nodes in a network can jointly produce one unit of surplus. A maximum number of linked nodes is selected in every period to bargain bilaterally over the division of the surplus, according to the protocol proposed by Rubinstein and Wollinsky [Equilibrium in a market with sequential bargaining, Econometrica 53 (1985) 1133–1150]. All pairs, which reach an agreement, obtain the (discounted) payoffs and are removed from the network. This bargaining game has a unique subgame perfect equilibrium that induces the Dulmage–Mendelsohn decomposition (partition) of the bipartite network (of the set of nodes in this network).

Is the general public licence a rational choice

Open source projects are networks of developers, distributors and end-users of non-proprietary created knowledge goods. It has been argued that this form of organization has some advantages over the firm or market coordination. I show that for sufficiently convex and modular projects, proprietary licences are not able to sustain sequential knowledge production which, however, can be carried out if the project is run on the open source basis. Copyright 2007 Blackwell Publishing Ltd..

Markets, Bargaining, and Networks with Heterogeneous Agents

The paper proposes an intertemporal model of bargaining among heterogeneous buyers and sellers placed on a bipartite network. First, it characterizes conditions on the network under which its trading restrictions are inessential and the outcome is arbitrage-free. Instead, when the system is segmented in different trading components, we show how these come about and how prices are determined in each of them. Second, we turn to the issue of network endogeneity, focusing on those networks that are Pairwise Stable. Such networks are shown to always exist and be arbitrage-free. In the latter respect, therefore, they satisfy one of the key properties displayed by frictionless markets. We identify, however, a sharp contrast regarding another key feature: Pairwise-Stable networks are generically inefficient if the matching process is genuinely decentralized. This uncovers a fundamental incompatibility between individual incentives and social welfare in endogenous trading networks. We explain that such incompatibility is not only due to buyer/seller heterogeneity but is also caused by the incentives underlying network formation in a trading context.

Endogenous Two-Sided Markets with Repeated Transactions

We consider homogeneous two-sided markets, in which connected buyer-seller pairs bargain and trade repeatedly. In this infinite market game with exogenous matching probabilities and a common discount factor, we prove the existence of equilibria in stationary strategies. The equilibrium payoffs are given implicitly as a solution to a system of linear equations. Then, we endogenize the matching mechanism in a link formation stage that precedes the market game. When agents are sufficiently patient and link costs are low, we provide an algorithm to construct minimally connected networks that are pairwise stable with respect to the expected payoffs in the trading stage. The constructed networks are essentially efficient and consist of components with a constant buyer-seller ratio. The latter ratio increases (decreases) for a buyer (seller) that deletes one of her links in a pairwise stable component.

Dynamic multilateral markets

We study dynamic multilateral markets, in which players’ payoffs result from intra-coalitional bargaining. The latter is modeled as the ultimatum game with exogenous (time-invariant) recognition probabilities and unanimity acceptance rule. Players in agreeing coalitions leave the market and are replaced by their replicas, which keeps the pool of market participants constant over time. In this infinite game, we establish payoff uniqueness of stationary equilibria and the emergence of endogenous cooperation structures when traders experience some degree of (heterogeneous) bargaining frictions. When we focus on market games with different player types, we derive, under mild conditions, an explicit formula for each type’s equilibrium payoff as the market frictions vanish.

A decentralized model of information pricing in networks

We propose a recursive method of pricing an information good in a network of holders and demanders of this good. The prices are determined via a unique equilibrium outcome in a sequence of bilateral bargaining games that are played by connected agents. If the information is a homogenous, non-depreciating good without network effects, we derive explicit formulae which elucidate the role of the link pattern among the players. Particularly, we find out that the equilibrium price is intimately related to the existence of cycles in the network: it is zero if a cycle covers the trading pair and it is proportional to the direct and indirect utility that the good generates otherwise.

Voting rules and efficiency in one-dimensional bargaining games with endogenous protocol

We analyze a rent-seeking contest that determines the bargaining protocol in a one-dimensional bargaining game, where agents preferences over social outcomes are single-peaked. We relate the incentives of agents to make unproductive and costly efforts/investments to the quota rules that are required to implement agreements. When the contest assigns persistent recognition probabilities, we find that simple majority minimizes the total investments and, hence, inefficiency. In case that the contest recurs each period, multiple equilibria exist with the particularity that in each equilibrium only one agent controls the agenda of the bargaining process.

Volatility–volume co-movements: evidence from China metal markets

ABSTRACT This article investigates the interactional relationship between price volatility and futures trading activity for three heavily traded metal products on the Shanghai Metal Exchange and the Shanghai Futures Exchange. Using models based on vector autoregression and generalized method of moments, we show, in particular, that futures trading activity has a strong impact on both spot and futures price volatility in copper and aluminium markets. Futures trading activity leads spot market volatility in copper and aluminium markets which suggests that futures markets have a destabilizing effect. In order to disentangle the effect of different traders’ types on asset price movements, we decompose futures trading into speculators’ and hedgers’ trading and investigate their contributions to volatility. As a robustness check, we investigate the impact of endogenous structural breaks on the interactional relationship between price volatility and futures trading.

Multidimensional Risk and Risk Dependence

Evaluating multiple sources of risk is an important problem with many applications in finance and economics. In practice this evaluation remains challenging. We propose a simple non-parametric framework with several economic and statistical applications. In an empirical study, we illustrate the flexibility of our technique by applying it to the evaluation of multidimensional density forecasts, multidimensional Value at Risk and dependence in risk.

Recovering Social Networks from Individual Attributes

One of the most important challenges of network analysis remains the scarcity of reliable information on existing connection structures. This work explores theoretical and empirical methods of inferring directed networks from nodes attributes and from functions of these attributes that are computed for connected nodes. We discuss the conditions, under which an underlying connection structure can be (probabilistically) recovered, and propose a Bayesian recovery algorithm. In an empirical application, we test the algorithm on the data from the European School Survey Project on Alcohol and Other Drugs.