Learning the optimal buffer-stock consumption rule of Carroll

This article questions the rather pessimistic conclusions of Allen et Carroll (2001) about the ability of consumer to learn the optimal buffer-stock based consumption rule. To this aim, we develop an agent based model where alternative learning schemes can be compared in terms of the consumption behaviour that they yield. We show that neither purely adaptive learning, nor social learning based on imitation can ensure satisfactory consumption behaviours. By contrast, if the agents can form adaptive expectations, based on an evolving individual mental model, their behaviour becomes much more interesting in terms of its regularity, and its ability to improve performance (which is as a clear manifestation of learning). Our results indicate that assumptions on bounded rationality, and on adaptive expectations are perfectly compatible with sound and realistic economic behaviour, which, in some cases, can even converge to the optimal solution. This framework may therefore be used to develop macroeconomic models with adaptive dynamics.Consumption decisions; Learning; Expectations; Adaptive behaviour; Computational economics

Monetary Policy Rules, Learning and Stability: a Survey of the Recent Literature (In French)

This paper presents the literature about econometric learning and its impact on the performances of monetary policy rules in the framework of the new canonical macroeconomic model. Rational expectations which are a building block of the original model can thus be replaced by expectations based on estimation algorithms. The permanent updating of these estimations can be interpreted as a learning proces of the model’s agents. This learning proces induces additional dynamics into the model. The literature in question uses two criteria in order to analyse the ability of monetary policy rules to stabilise the economy: (i) uniqueness of the rational expectations equilibrium in the original model and (ii) stability in regards to learning in the modified model. Taking learning into account enables to detect shortcomings of a rule according to (ii) that would not been seen in a rational expectations model. However, the main message of the surveyed literature is that most of the results found in a rational expectations framework are robust. The paper ends with a discussion on the specific problems met in the introduction of a learning proces in the new canonical model.monetary policy rules – learning – determination - stability

Are automotive global production networks becoming more global? Comparison of regional and global integration processes based on auto parts trade data

In this paper, we examine the evolution of international exchanges of auto parts over the 2000-2012 period. The first part of our study proposes an analysis of the organisation of automotive supply chains based on the global production networks framework. We give details about this approach by stating the nature of trade flows that occur in these networks, and by highlighting the importance of intra-firms flows. The second part poses the question of reasons for an eventual increase of intercontinental flows at the expense of intra-continental flows. In the third part, we evaluate the assumptions made in this context. On the basis of Chelem data about auto parts exchanges, we examine in a comparative way the evolution of intra-continental and intercontinental flows for nine zones of regional integration that cover the world’s entire set of countries. Our results highlight the heterogeneity of situations and of trajectories in the different zones. We explain this state of affairs by the history and the trajectory of the industrial actors, by institutional opportunities/constraints, and by the balance of power between the industries engaged in the setting up of automotive production networks

Gibrat’s law, Zipf’s law and Cointegration

This paper examines the methods to detect the nature of the urban growth processes. It seems that cointegration testing enables to disentangle two versions of Gibrat’s law: a first one with growth shocks that are iid across time and cities (implying convergence of the city-size distribution towards Zipf’s law), and an alternative one with growth shocks that are only iid over time (implying conservation of the initial structure of the city size distribution)

Gibrat’s law, Zipf’s law and Cointegration

This paper examines the methods to detect the nature of the urban growth processes. It seems that cointegration testing enables to disentangle two versions of Gibrat’s law: a first one with growth shocks that are iid across time and cities (implying convergence of the city-size distribution towards Zipf’s law), and an alternative one with growth shocks that are only iid over time (implying conservation of the initial structure of the city size distribution)

How does regulation affect beliefs ? Stock Market valuation of Orphan Drug Regulatory Approvals:(112th 2016 APSA Annual Meeting)

1st lines: 1. Regulation and Industry Change: reversing cause and effect The link between the evolution of regulatory institutions and the development of new schemes for value creation within an industry (i.e, its business model) has most often been studied from the angle of how sectorial change has affected the institutionalization of new policy instruments. More precisely, the line of questioning generally adopted has been whether or not political actors have sought to simply follow long term trends within an industrial sector - e.g., technological breaks or the evolving structure of innovation (Aghion and Howitt 1992), its exogenous conditions (Kane 1981) and more recently, economic crisis (Tirole 2012) - by creating an appropriate regulatory framework, consistent with the new environment in which private actors operate. If bureaucrats or politicians appear to have failed to ensure that new processes of value creation are translated into regulatory institutions that match the dynamics of the sector in question, other scholars regularly allege the capture of the political process by interest groups (Carpenter and Moss 2014)

Learning the optimal buffer-stock consumption rule of Carroll

This article questions the rather pessimistic conclusions of Allen et Carroll (2001) about the ability of consumer to learn the optimal buffer-stock based consumption rule. To this aim, we develop an agent based model where alternative learning schemes can be compared in terms of the consumption behaviour that they yield. We show that neither purely adaptive learning, nor social learning based on imitation can ensure satisfactory consumption behaviours. By contrast, if the agents can form adaptive expectations, based on an evolving individual mental model, their behaviour becomes much more interesting in terms of its regularity, and its ability to improve performance (which is as a clear manifestation of learning). Our results indicate that assumptions on bounded rationality, and on adaptive expectations are perfectly compatible with sound and realistic economic behaviour, which, in some cases, can even converge to the optimal solution. This framework may therefore be used to develop macroeconomic models with adaptive dynamics.Consumption decisions; Learning; Expectations; Adaptive behaviour, Computational economics

Assessment of female reproductive status by male longtailed macaques, Macaca fascicularis, under natural conditions

Recent theories on primate sexual selection have paid increasing attention to the importance of reproductive strategies of females living in multimale groups. However, the extent to which females are able effectively to conceal or advertise the time of ovulation as part of these strategies remains unclear. Few studies have investigated the ability of males to discern female reproductive status under natural conditions, and none has taken into account differences in male rank, and thus ability to gain access to females or cues. We tested male assessment of a female's fertile phase under natural conditions in longtailed macaques. We used timing of mate guarding by dominant males and the response of subordinate males towards the repeated playback of a female copulation call to measure male interest in females throughout the ovarian cycle. Relating the degree of male interest to female reproductive status, as determined noninvasively by faecal hormone analysis, we found that interest in females shown by both dominant and subordinate males was strongest during and around the fertile phase. Our results also indicate that males were better able to recognize the fertile period in conception than in nonconception cycles. Furthermore, our finding of a strong positive relation between male interest and female oestrogen levels in all cycles indicates that at least some of the cues used by males to assess female reproductive status are oestrogen related

Règles de politique monétaire, apprentissage et stabilité : une revue de la littérature récente

Cahiers du GREThA n° 2010-0