Heterogeneity and Aggregation in a Financial Accelerator Model

In this paper we present a macroeconomic model in which changes in the variance (and higher moments of the distribution) of firm's financial conditions - i.e. "distributive shocks" - are bound to play a crucial role in the determination of output fluctuations. Firms differ by degree of financial robustness, which affects (optimal) investment in a bankruptcy risk context (à la Greenwald-Stiglitz). As to households, for the sake of simplicity, we assume that they are homogeneous in every respect so that we can adopt the representative agent hypothesis. We can explore the properties of the macro-dynamic model either via the study of the two-dimensional map defining the laws of motion of the average equity ratio and of the variance of the distribution or via simulations in a multiagent framework.

Asset Prices and Monetary Policy: A New View of the Cost Channel

Should the central bank act to prevent "excessive" asset price dynamics or should it wait until the boom spontaneously turns into a crash and intervene afterwards to attenuate the fallout on the real economy? The standard "three equation" New Keynesian framework is inadequate to analyse this issue for the very simple reason that asset prices are not explicitly included in the model. There are two straightforward ways to take into account asset price dynamics in this framework. First of all, the objective function of the central bank - usually defined in terms of inflation and the output gap - could be "augmented" to take into account asset price inflation. Second, expected asset price inflation can affect the IS curve through a wealth effect. In this paper we follow a different route. In our model in fact, the expected asset price dynamics will be eventually incorporated into the NK Phillips curve. This is due to the assumption of a cost channel for monetary policy which is activated whenever monetary policy affects asset prices and dividends. In fact they determine the cost of external finance in the simple "equity only" financing model we consider, abstracting for simplicity from internal funds and the credit market.

"Credit Cycle" in an OLG Economy with Money and Bequest

In the late '90s Kiyotaki and Moore (KM) put forward a new framework (Kiyotaki and Moore,1997) to explore the Financial Accelerator hypothesis. The original model was framed in an Infinitely Lived Agent context (ILA-KM economy). As in KM we develop a dynamic model in which the durable asset ("land") is not only an input but also collateralizable wealth to secure lenders from the risk of borrowers' default. In this paper, however, we model an OLG-KM economy whose novel feature is the role of money as a store of value and of bequest as a vehicle of resources to be "invested" in landholding. The dynamics generated by the model are complex. Not only cyclical patterns are routinely generated but the periodicity and amplitude are irregular. A route to chaotic dynamics is open.

Reflections on Modern Macroeconomics: Can We Travel Along a Safer Road?

In this paper we sketch some reflections on the pitfalls and inconsistencies of the research program - currently dominant among the profession - aimed at providing microfoundations to macroeconomics along a Walrasian perspective. We argue that such a methodological approach constitutes an unsatisfactory answer to a well-posed research question, and that alternative promising routes have been long mapped out but only recently explored. In particular, we discuss a recent agent-based, truly non-Walrasian macroeconomic model, and we use it to envisage new challenges for future research.Comment: Latex2e v1.6; 17 pages with 4 figures; for inclusion in the APFA5 Proceeding

Self-organized model of cascade spreading

We study simultaneous price drops of real stocks and show that for high drop thresholds they follow a power-law distribution. To reproduce these collective downturns, we propose a minimal self-organized model of cascade spreading based on a probabilistic response of the system elements to stress conditions. This model is solvable using the theory of branching processes and the mean-field approximation. For a wide range of parameters, the system is in a critical state and displays a power-law cascade-size distribution similar to the empirically observed one. We further generalize the model to reproduce volatility clustering and other observed properties of real stocks.Comment: 8 pages, 6 figure

An agent based decentralized matching macroeconomic model

In this paper we present a macroeconomic microfounded framework with heterogeneous agents-individuals, firms, banks-which interact through a decentralized matching process presenting common features across four markets-goods, labor, credit and deposit. We study the dynamics of the model by means of computer simulation. Some macroeconomic properties emerge such as endogenous business cycles, nominal GDP growth, unemployment rate fluctuations, the Phillips curve, leverage cycles and credit constraints, bank defaults and financial instability, and the importance of government as an acyclical sector which stabilize the economy. The model highlights that even extended crises can endogenously emerge. In these cases, the system may remain trapped in a large unemployment status, without the possibility to quickly recover unless an exogenous intervention takes place

Explaining persistent cycles in a short-run context: firms’ propensity to invest and omnipotent shareholders

In this article, we develop a standard short-run Kaleckian macromodel. First, we study the stability of equilibrium and make some comparative static exercises. Then, we take into account different specifications for an endogenous propensity to invest and systematically analyze the short-run dynamics of the model. We show that when firms’ managers adopt abnormal behaviours due to pressures from shareholders regarding the propensity to invest the system exhibits persistent cycles and chaotic trajectories. The analysis emphasizes that, even in the short-run, shareholders may generate instability which represents a serious threat that should not be underestimated for a capitalist economy

Crises: Principles and Policies: With an Application to the Eurozone Crisis

Economies around the world have faced repeated crises — more frequently over the past thirty years. The fact that they have become more frequent and pervasive at the same time that we believe we have learned more about the management of the economy and as markets have seemingly improved poses a puzzle: shouldn't rational markets avoid these catastrophes, the costs of which outweigh, by an enormous amount, any benefit that might have accrued to the economy from the actions prior to the crisis that might have contributed to it? This is especially true of the large fraction of crises that can be called “debt crises,” precipitated by a country’s difficulty in repaying what it owes. The benefits of income smoothing (arising from the difference in the marginal utility of income in periods when income is low and when income is high) are overwhelmed by the social and economic costs of the ensuing crisis