Microeconomic Structure determines Macroeconomic Dynamics. Aoki defeats the Representative Agent

Masanao Aoki developed a new methodology for a basic problem of economics: deducing rigorously the macroeconomic dynamics as emerging from the interactions of many individual agents. This includes deduction of the fractal / intermittent fluctuations of macroeconomic quantities from the granularity of the mezo-economic collective objects (large individual wealth, highly productive geographical locations, emergent technologies, emergent economic sectors) in which the micro-economic agents self-organize. In particular, we present some theoretical predictions, which also met extensive validation from empirical data in a wide range of systems: - The fractal Levy exponent of the stock market index fluctuations equals the Pareto exponent of the investors wealth distribution. The origin of the macroeconomic dynamics is therefore found in the granularity induced by the wealth / capital of the wealthiest investors. - Economic cycles consist of a Schumpeter 'creative destruction' pattern whereby the maxima are cusp-shaped while the minima are smooth. In between the cusps, the cycle consists of the sum of 2 'crossing exponentials': one decaying and the other increasing. This unification within the same theoretical framework of short term market fluctuations and long term economic cycles offers the perspective of a genuine conceptual synthesis between micro- and macroeconomics. Joining another giant of contemporary science - Phil Anderson - Aoki emphasized the role of rare, large fluctuations in the emergence of macroeconomic phenomena out of microscopic interactions and in particular their non self-averaging, in the language of statistical physics. In this light, we present a simple stochastic multi-sector growth model.Comment: 42 pages, 6 figure

The network origins of aggregate fluctuations

This paper argues that in the presence of intersectoral input-output linkages, microeconomic idiosyncratic shocks may lead to aggregate fluctuations. In particular, it shows that, as the economy becomes more disaggregated, the rate at which aggregate volatility decays is determined by the structure of the network capturing such linkages. Our main results provide a characterization of this relationship in terms of the importance of different sectors as suppliers to their immediate customers as well as their role as indirect suppliers to chains of downstream sectors. Such higher-order interconnections capture the possibility of "cascade effects" whereby productivity shocks to a sector propagate not only to its immediate downstream customers, but also indirectly to the rest of the economy. Our results highlight that sizable aggregate volatility is obtained from sectoral idiosyncratic shocks only if there exists significant asymmetry in the roles that sectors play as suppliers to others, and that the "sparseness" of the input-output matrix is unrelated to the nature of aggregate fluctuations.Business cycle, aggregate volatility, diversification, input-output linkages, intersectoral network, cascades

The Paradoxical Fate of the Representative Firm

While modern theorising on the microfoundation of macroeconomics makes intense use of the representative firm notion, severe objections have been raised. Regarded from the history of thought this is the second time that its usefulness is called into question. The paper presents an old literature which has ended with the abandonment of the representative firm from competition theory because it neglects the innovation issue. It shows that its subsequent adoption to macroeconomics suffers from similar flaws. It follows that the representative firm is inappropriate for the analysis of modern competitive economies and should be withdrawn from macroeconomics as well.microfoundation, representative agent, aggregation, innovation, competition, Marshall, Schumpeter

The Theorem of Proportionality in Mainstream Capital Theory: An Assessment of its Conceptual Foundations

It is ascertained that the theorem of proportionality, which maintains that replacement investment is a constant proportion of the outstanding capital stock, has several fundamental shortcomings. It derives from a model founded on assumptions that are highly restrictive and unlikely to hold in reality. It is alien to the thinking of researchers in industrial organization and other neighboring fields to economics that treat the durability of capital goods as a choice variable. It ignores several thorny conceptual and methodological issues and, perhaps most important, it may have restrained seriously the progress towards developing models based on more realistic approaches of production. However, despite its shortcomings, the theorem continues to dominate mainstream capital theory, most probably because of: a) its simplicity, and b) the lack of a model that might yield a better theorem in terms of standard criteria, like explanatory and predictive power, simplicity, fruitfulness, etc. For this reason attention is drawn to recent research which shows that a model centered on the heterogeneous structure of capital and the useful lives of its components is both feasible and exceedingly rich in theoretical and empirical implications.Capital longevity, replacement, depreciation, scrappage, maintenance, utilization, obsolescence.

The Network Origins of Large Economic Downturns

This paper shows that large economic downturns may result from the propagation of microeconomic shocks over the input-output linkages across different firms or sectors within the economy. Building on the framework of Acemoglu et al. (2012), we argue that the economy’s input-output structure can fundamentally reshape the distribution of aggregate output, increasing the likelihood of large downturns from infinitesimal to substantial. More specifically, we show that an economy with non-trivial intersectoral input-output linkages that is subject to thin-tailed productivity shocks may exhibit deep recessions as frequently as economies that are subject to heavy-tailed shocks. Moreover, we show that in the presence of input-output linkages, aggregate volatility is not necessarily a sufficient statistic for the likelihood of large downturns. Rather, depending on the shape of the distribution of the idiosyncratic shocks, different features of the economy’s input-output network may be of first-order importance. Finally, our results establish that the effects of the economy’s input-output structure and the nature of the idiosyncratic firm level shocks on aggregate output are not separable, in the sense that the likelihood of large economic downturns is determined by the interplay between the two

The Theorem of Proportionality in Mainstream Capital Theory: An Assessment of its Applicability

This paper surveys and assesses the empirical literature that bears on the applicability of the theorem of proportionality, which asserts that depreciation is proportional to the outstanding capital stock. All available evidence shows that: a) the rates of depreciation and retirements vary from year to year in response to changes in conventional economic forces like utilization, maintenance and repair, the prices of new capital goods, etc., and b) while the approximation of the distribution of depreciation rates by a single parameter may be characterized by simplicity and ease of use, at the same time it thwarts the advances that can be achieved by returning to a general equilibrium model centered on the time structure of capital and the useful lives of its components. For this reason, it is concluded that, the sooner this theorem is replaced by an endogenous theory of depreciation and replacement, the better for economic theory and policy.Capital longevity, replacement, depreciation, scrappage, maintenance, utilization, obsolescence

Business surveys modelling with Seasonal-Cyclical Long Memory models.

Business surveys are an important element in the analysis of the short-term economic situation because of the timeliness and nature of the information they convey. Especially, surveys are often involved in econometric models in order to provide an early assessment of the current state of the economy, which is of great interest for policy-makers. In this paper, we focus on non-seasonally adjusted business surveys relative to the Euro area released by the European Commission. We introduce an innovative way for modelling those series taking the persistence of the seasonal roots into account through seasonal-cyclical long memory models. We empirically prove that such models produce more accurate forecasts than classical seasonal linear models.Euro area ; business surveys ; seasonal ; long memory.