Publications

Summary

This chapter surveys work dedicated to macroeconomic analysis using an agent- based modeling approach. After a short review of the origins and general characteristics of this approach a systemic comparison of the structure and modeling assumptions of a set of important (families of) agent-based macroeconomic models is provided. The comparison highlights substantial similarities between the different models, thereby identifying what could be considered an emerging common core of macroeconomic agent-based modeling. In the second part of the chapter agent-based macroeconomic research in different domains of economic policy is reviewed.

Summary

We investigate, compare, and contrast the emerging properties of a macroeconomic agent-based model along the lines of Assenza et al., (2015, Journal of Economic Dynamics and Control, 50, 5–28) when the government experiments with different policy configurations: (i) tax and transfer; (ii) tax, transfer, and spend; and (iii) the implementation of a fiscal rule, such as a stylized Stability and Growth Pact. In some of the scenarios considered, a remarkable property can be detected, which we label the balanced budget emerging property: The scale of activity in the aggregate (GDP, employment, and unemployment rate) is such that a balanced budget emerges spontaneously. The strong implication of this property is that the fiscal authority is able to target GDP and the unemployment rate, a result reminiscent of the Blinder–Solow framework. It is worth noting, however, that there are many departures from the rule, which we have detected by carrying out the sensitivity analysis.

Summary

Classifying movement behaviour of marine predators in relation to anthropogenic activity and environmental conditions is important to guide marine conservation. We studied the relationship between grey seal (Halichoerus grypus) behaviour and environmental variability in the southwestern Baltic Sea where seal-fishery conflicts are increasing. We used multiple environmental covariates and proximity to active fishing nets within a multivariate hidden Markov model (HMM) to quantify changes in movement behaviour of grey seals while at sea. Dive depth, dive duration, surface duration, horizontal displacement, and turning angle were used to identify travelling, resting and foraging states. The likelihood of seals foraging increased in deeper, colder, more saline waters, which are sites with increased primary productivity and possibly prey densities. Proximity to active fishing net also had a pronounced effect on state …

Summary

We present a continuous-time generalization of the seminal research and development model of d’Aspremont and Jacquemin (Am Econ Rev 78(5):1133–1137, 1988) to examine the trade-off between the benefits of allowing firms to cooperate in research and the corresponding increased potential for product market collusion. We show the existence of a solution to the optimal investment problem using a combination of results from viscosity theory and the theory of planar dynamical systems. In particular, we show that there is a critical level of marginal cost at which firms are indifferent between doing nothing and starting to develop the technology. We find that colluding firms develop further a wider range of initial technologies, pursue innovations more quickly, and are less likely to abandon a technology. Product market collusion could thus yield higher total surplus.

Summary

We consider a model of influence with a set of nonstrategic agents and two strategic agents. The nonstrategic agents have initial opinions and are linked through a simply connected network. They update their opinions as in the DeGroot model. The two strategic agents have fixed and opposed opinions. They each form a link with a nonstrategic agent in order to influence the average opinion that emerges due to interactions in the network. This procedure defines a zero-sum game whose players are the two strategic agents and whose strategy set is the set of nonstrategic agents. We focus on the existence and the characterization of pure strategy equilibria in this setting. Simple examples show that the existence of a pure strategy equilibrium does depend on the structure of the network. We characterize equilibrium with two notions: the influenceability of target agents, and their centrality, which in our context we call “intermediacy.” We also show that when the two strategic agents have the same impact, symmetric equilibria emerge as natural solutions. In the case where the impacts are uneven, the game has only equilibria in mixed strategies, the high impact agent focuses on his own centrality/intermediacy and the influenceability of his opponent’s target while the low influence agent focuses on the influenceability of his own target.

Summary

We examine to what extent market conditions facilitating start-up formation affect firms' R&D investment and profits. We consider a model in which R&D efforts of an incumbent firm generate partly tacit technological know-how embodied in a key R&D employee, who might use it to form a start-up. The availability of complementary assets influences whether new firms are created and determine expected profits for start-up's founders. A large availability of complementary assets has the direct effect that the generation of start-ups is fostered. However, as a strategic effect, the incentives of incumbents to invest in R&D may be reduced because of the increased danger of knowledge loss occurring through start-up formation. We characterize the effects of an increase in the availability of complementary assets, showing that counter-intuitively there are cases in which it induces an increase in incumbents' R&D investment.

Summary

Two agents endowed with different categorisations engage in bargaining to reach an understanding and agree on a common categorisation. We model the process as a simple non-cooperative game and demonstrate three results. When the initial disagreement is focused, the bargaining process has a zero-sum structure. When the disagreement is widespread, the zero-sum structure disappears and the unique equilibrium requires a retraction of consensus: two agents who individually associate a region with the same category end up rebranding it under a different category. Finally, we show that this last equilibrium outcome is Pareto dominated by a cooperative solution that avoids retraction; that is, the unique equilibrium agreement may be inefficient.

Summary

We study information acquisition in a flexible framework with strategic complementarity or substitutability in actions and a rich set of externalities that are responsible for possible wedges between the equilibrium and the efficient acquisition of information. First, we relate the (in)efficiency in the acquisition of information to the (in)efficiency in the use of information and explain why efficiency in the use does not guarantee efficiency in the acquisition. Next, we show how the acquisition of private information affects the social value of public information (i.e., the comparative statics of equilibrium welfare with respect to the quality of public information). Finally, we illustrate the implications of our results in a few applications that include beauty contests, monetary economies with price-setting complementarities, and economies with negative production externalities

Summary

This paper investigates firms׳ optimal location choices explicitly accounting for the role of inwards and outwards knowledge spillovers in a dynamic Cournot oligopoly with firms that are heterogeneous in their ability to carry out cost-reducing R&D. Firms can either locate in an industrial cluster or in isolation. Technological spillovers are exchanged between the firms located in the cluster. It is shown that a technological leader has an incentive to locate in isolation only if her advantage exceeds a certain threshold, which is increasing in firms׳ discount rate, in industry dispersion, and in the intensity of knowledge spillovers. Scenarios are identified where although it is optimal for the technological leader to locate in isolation, from a welfare perspective it would be desirable that she locates in the cluster.

Summary

It is notoriously difficult to predict the behaviour of a complex self-organizing system, where the interactions among dynamical units form a heterogeneous topology. Even if the dynamics of each microscopic unit is known, a real understanding of their contributions to the macroscopic system behaviour is still lacking. Here, we develop information-theoretical methods to distinguish the contribution of each individual unit to the collective out-of-equilibrium dynamics. We show that for a system of units connected by a network of interaction potentials with an arbitrary degree distribution, highly connected units have less impact on the system dynamics when compared with intermediately connected units. In an equilibrium setting, the hubs are often found to dictate the long-term behaviour. However, we find both analytically and experimentally that the instantaneous states of these units have a short-lasting effect on the state trajectory of the entire system. We present qualitative evidence of this phenomenon from empirical findings about a social network of product recommendations, a protein–protein interaction network and a neural network, suggesting that it might indeed be a widespread property in nature.