Publications

Publications

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2021 / Hommes, C.

Behavioral and Experimental Macroeconomics and Policy Analysis: A Complex Systems Approach

Journal of Economic Literature, Vol. 59(1), 149–219
Summary
This survey discusses behavioral and experimental macroeconomics, emphasizing a complex systems perspective. The economy consists of boundedly rational heterogeneous agents who do not fully understand their complex environment and use simple decision heuristics. Central to our survey is the question of under which conditions a complex macro-system of interacting agents may or may not coordinate on the rational equilibrium outcome. A general finding is that under positive expectations feedback (strategic complementarity)—where optimistic (pessimistic) expectations can cause a boom (bust)—coordination failures are quite common. The economy is then rather unstable, and persistent aggregate fluctuations arise strongly amplified by coordination on trend-following behavior leading to (almost-)self-fulfilling equilibria. Heterogeneous expectations and heuristics switching models match this observed micro and macro behavior surprisingly well. We also discuss policy implications of this coordination failure on the perfectly rational aggregate outcome and how policy can help to manage the self-organization process of a complex economic system. (JEL C63, C90, D91, E12, E71, G12)
2020 / Corrocher N., G. Cecere and M. L. Mancusi

Financial constraints and public funding of eco-innovation: Empirical evidence from European SMEs

Small Business Economics, Vol. 54, 285-302
Summary
Financial constraints have an important impact on the development of eco-innovations but their effect varies according to the type of funding. This article studies the interaction between public funding on the one hand, and internal and external lack of funding on the other. The empirical analysis is based on a sample of European small- and medium-sized enterprises, and exploits information on firms’ involvement in eco-innovation activities, their drivers, and obstacles. Our results show that, even accounting for demand-pull effects and regulatory interventions, access to public funds and fiscal incentives is effective for improving the firm’s ability to introduce eco-innovations, particularly if the company has ample funds from either internal or external sources. Our findings suggest also that public funding is perceived by firms as complementary to other external finance.
2021 / Konc T., I. Savin and J. van den Bergh

The social multiplier of environmental policy: application to carbon taxation

Journal of Environmental Economics and Management, 105
Summary
We analyze the effectiveness of environmental policy when consumers are subject to social influence. To this end, we build a model of consumption decisions driven by socially-embedded preferences formed under the influence of peers in a social network. This setting gives rise to a social multiplier of environmental policy. In an application to climate change, we derive Pigouvian and target-achieving carbon taxes under socially-embedded preferences. Under realistic assumptions the social multiplier is equal to 1.30, allowing to reduce the effective tax by 38%. We show that the multiplier depends on four factors: strength of social influence, initial taste distribution, network topology and income distribution. The approach provides a basis for rigorously analyzing a transition to low-carbon lifestyles and identifying complementary information and network policies to maximize the effectiveness of carbon taxation.
2020 / Bao, T., M. Hennequin, C. Hommes and D. Massaro

Coordination on bubbles in large-group asset pricing experiments

Journal of Economic Dynamics and Control, Vol. 110, Art.-Nr. 103702
Summary
We present a large-group experiment in which participants predict the price of an asset, whose realization depends on the aggregation of individual forecasts. The markets consist of 21 to 32 participants, a group size larger than in most experiments. Multiple large price bubbles occur in six out of seven markets. The bubbles emerge even faster than in smaller markets. Individual forecast errors do not cancel out at the aggregate level, but participants coordinate on a trend-following prediction strategy that gives rise to large bubbles. The observed price patterns can be captured by a behavioral heuristics switching model with heterogeneous expectations.
2020 / Castro J., Drews S., Exadaktylos F., Foramitti J., Klein F., Konc T., Savin I. and van den Bergh J.

A review of agent-based modelling of climate-energy policy

WIREs Climate Change, Vol. 11, Issue 4
Summary
Agent‐based models (ABMs) have recently seen much application to the field of climate mitigation policies. They offer a more realistic description of micro behavior than traditional climate policy models by allowing for agent heterogeneity, bounded rationality and nonmarket interactions over social networks. This enables the analysis of a broader spectrum of policies. Here, we review 61 ABM studies addressing climate‐energy policy aimed at emissions reduction, product and technology diffusion, and energy conservation. This covers a broad set of instruments of climate policy, ranging from carbon taxation, and emissions trading through adoption subsidies to information provision tools such as smart meters and eco‐labels. Our treatment pays specific attention to behavioral assumptions and the structure of social networks. We offer suggestions for future research with ABMs to answer neglected policy questions.
2020 / Pieschner S. and C. Fuchs

Bayesian inference for diffusion processes: using higher-order approximations for transition densities

Royal Society Open Science, Vol. 7, Issue 10
Summary
Modelling random dynamical systems in continuous time, diffusion processes are a powerful tool in many areas of science. Model parameters can be estimated from time-discretely observed processes using Markov chain Monte Carlo (MCMC) methods that introduce auxiliary data. These methods typically approximate the transition densities of the process numerically, both for calculating the posterior densities and proposing auxiliary data. Here, the Euler–Maruyama scheme is the standard approximation technique. However, the MCMC method is computationally expensive. Using higher-order approximations may accelerate it, but the specific implementation and benefit remain unclear. Hence, we investigate the utilization and usefulness of higher-order approximations in the example of the Milstein scheme. Our study demonstrates that the MCMC methods based on the Milstein approximation yield good estimation results. However, they are computationally more expensive and can be applied to multidimensional processes only with impractical restrictions. Moreover, the combination of the Milstein approximation and the well-known modified bridge proposal introduces additional numerical challenges.
2020 / McClintock, B.T. , R. Langrock, O. Gimenez, E. Cam, D. L. Borchers, R. Glennie and T.A. Patterson

Uncovering ecological state dynamics with hidden Markov models

arXiv preprint arXiv:2002.10497
Summary
Ecological systems can often be characterised by changes among a set of underlying states pertaining to individuals, populations, communities, or entire ecosystems through time. Owing to the inherent difficulty of empirical field studies, ecological state dynamics operating at any level of this hierarchy can often be unobservable or" hidden". Ecologists must therefore often contend with incomplete or indirect observations that are somehow related to these underlying processes. By formally disentangling state and observation processes based on simple yet powerful mathematical properties that can be used to describe many ecological phenomena, hidden Markov models (HMMs) can facilitate inferences about complex system state dynamics that would otherwise be intractable. However, while HMMs are routinely applied in other disciplines, they have only recently begun to gain traction within the broader ecological community. We provide a gentle introduction to HMMs, establish some common terminology, and review the immense scope of HMMs for applied ecological research. By illustrating how practitioners can use a simple conceptual template to customise HMMs for their specific systems of interest, revealing methodological links between existing applications, and highlighting some practical considerations and limitations of these approaches, our goal is to help establish HMMs as a fundamental inferential tool for ecologists.
2020 / Pohle, J., R. Langrock, M. van der Schaar, R. King and F.H. Jensen

A primer on coupled state-switching models for multiple interacting time series

arXiv preprint arXiv:2004.14700
Summary
State-switching models such as hidden Markov models or Markov-switching regression models are routinely applied to analyse sequences of observations that are driven by underlying non-observable states. Coupled state-switching models extend these approaches to address the case of multiple observation sequences whose underlying state variables interact. In this paper, we provide an overview of the modelling techniques related to coupling in state-switching models, thereby forming a rich and flexible statistical framework particularly useful for modelling correlated time series. Simulation experiments demonstrate the relevance of being able to account for an asynchronous evolution as well as interactions between the underlying latent processes. The models are further illustrated using two case studies related to a) interactions between a dolphin mother and her calf as inferred from movement data; and b) electronic health record data collected on 696 patients within an intensive care unit.
2020 / Delli Gatti, D. and J. Grazzini

Rising to the challenge: Bayesian estimation and forecasting techniques for macroeconomic Agent Based Models

Journal of Economic Behavior & Organization, Vol. 178, 875-902
Summary
We propose two novel methods to “bring Agent Based Models (ABMs) to the data”. First, we describe a Bayesian procedure to estimate the numerical values of ABM parameters that takes into account the time structure of simulated and observed time series. Second, we propose a method to forecast aggregate time series using data obtained from the simulation of an ABM. We apply our methodological contributions to a specific medium-scale macro ABM.
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