Applying free random variables to random matrix analysis of financial data. Part I: The Gaussian case

We apply the concept of free random variables to doubly correlated (Gaussian) Wishart random matrix models, appearing, for example, in a multivariate analysis of financial time series, and displaying both inter-asset cross-covariances and temporal auto-covariances. We give a comprehensive introduction to the rich financial reality behind such models. We explain in an elementary way the main techniques of free random variables calculus, with a view to promoting them in the quantitative finance community. We apply our findings to tackle several financially relevant problems, such as a universe of assets displaying exponentially decaying temporal covariances, or the exponentially weighted moving average, both with an arbitrary structure of cross-covariances.     

An advanced multimedia infrastructure for WWW-based information systems

We present an advanced multimedia infrastructure that integrates continuous real-time media streams within the WWW. This new service architecture focuses on advanced facilities for dealing with multimedia contents. A mediation server is at the heart of the infrastructure. It organizes and structures the multimedia information space. In addition to simple services for accessing and delivering multimedia data, it provides new functionalities for filtering and querying multimedia content. Content servers and on-line sources deliver media streams integrated within synchronized multimedia presentations. We think that the infrastructure will offer new opportunities for WWW-based information systems and electronic commerce. This revised version was published online in June 2006 with corrections to the Cover Date.     

Investment and Finance in de novo private firms: Empirical Results from the Czech Republic, Hungary and Poland

In this paper we use a survey of 281 Czech, Hungarian and Polish newly-established small private firms in order to shed some light on the constraints these firms face in the credit market. The results of our survey show that imperfections in capital markets in Central European economies do not seem to actually inhibit the growth of new private firms. Credit markets do exist for de novo private firms in the three Central European transition economies studied, and they provide quite a large amount of financing from an early stage of the existence of firms. Financial intermediation works reasonably well as far as de novo private firms are concerned: loss-making de novo firms have a lower probability of getting credit than profitable ones. Banks protect themselves against the risk of a deteriorating pool of borrowers by requiring collateral for their loans. We do not find convincing evidence concerning the existence of adverse selection. Loss-making firms are not ready to pay higher interest rates than profitable firms and are not more likely to ask for credit than profitable firms.     

Consumers in transition from the centrally planned economy to the market economy

The article describes the development of consumption and the key consumer policy issues which stem from the transition of Central and East European economies from regimes of central planning to those of market economy. The author analyzes the role of the consumers in the evolution of the communist economies. His conclusion is that maintaining consumption at or below subsistence level (massive starvation was common) was one of the major sources of financing the USSR socialist industrialization under Stalin. This was not possible in the East European people's democracies and, after Stalin's death, in the USSR. Repressed inflation (permanent shortages of consumption goods) and foreign debt became new sources of financing growth in the later stages of the development of the communist economies, a development which caused a permanent disequilibrium leading to negative economic growth and massive popular revolt. The transition to the market economy makes it necessary to address these disequilibrium problems. Two transition strategies are discussed: gradual transition and shock treatment therapy. These strategies give rise to different consumer problems and to different sets of issues facing the consumer movement.

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Konsumenten im Übergang von der Planwirtschaft zur Marktwirtschaft

Zusammenfassung Der Beitrag beschreibt, wie sich der private Verbrauch beim Übergang von einer zentral geplanten Wirtschaft zu einer Marktwirtschaft in den osteuropäischen Staaten entwickelt und welche verbraucherpolitischen Aufgaben sich dabei ergeben.Der Autor beschäftigt sich mit der Rolle der Konsumenten in der Entwicklung der kommunistischen Gesellschaften in der UdSSR und in den östlichen Staaten Mitteleuropas. Er kommt zu dem Ergebnis, daß die Begrenzung des Verbrauches auf das Existenzminimum oder auf ein Niveau darunter (massive Hungersnöte waren verbreitet) ursprünglich eine der wichtigsten Quellen war, aus denen das Programm der sozialistischen Industrialisierung in der UdSSR unter Stalin finanziert wurde. Dieses Modell einer industriellen Entwicklung ließ sich in den anderen europäischen kommunistischen Staaten nicht durchführen und war nach Stalins Tod auch in der UdSSR nicht mehr möglich. In der Folgezeit wurden eine unterdrückte Inflation in der Form von dauerhafter Knapphiet von Konsumgütern und wachsende Auslandsschulden neue Quellen für die Finanzierung des industriellen Wachstums — eine Entwicklung, die ihre eigenen Ziele auf Dauer nicht erreichen konnte. Sie führte gegen Ende der 80iger Jahre zu negativen Wachstumsraten, zu massiver Unzufriedenheit in der Bevölkerung, zu sehr ernsthaften Umweltproblemen und zu riesigen Auslandsschulden. Versuche, die kommunistischen Volkswirtschaften zu reformieren ohne Veränderung der politischen und ideologischen Grundlagen, schlugen völlig fehl.Der Beitrag diskutiert zwei Strategien für den Übergang in das neue Wirtschaftssystem. Die eine ist der ungarische Weg eines allmählichen Überganges mit der Fortsetzung der Reformen, die noch unter kommunistischer Herrschaft begonnen wurden, und der allmählichen Öffnung für die Kräfte des Marktes. Die andere ist die polnische Form einer Schocktherapie mit abrupter völliger Öffnung gegenüber den Kräften des Marktes. Beide Strategien führen zu jeweils verschiedenen Verbraucherproblemen mit unterschiedlichen Anforderungen an die Verbraucherpolitik.

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Andrzej K. Kozminski is Professor and Chair of the Department of Management and Organization in the School of Management of Warsaw University, Director of the Warsaw University Postgraduate International Management Center, and President of the International Business School, Nowy Swiat 4, 00-497 Warsaw, Poland.     

A Bayesian method of combining judgmental and model-based density forecasts

This paper introduces a formal method of combining expert and model density forecasts when the sample of past forecasts is unavailable. It works directly with the expert forecast density and endogenously delivers weights for forecast combination, relying on probability rules only. The empirical part of the paper illustrates how the framework can be applied in forecasting US inflation by mixing density forecasts from an autoregressive model and the Survey of Professional Forecasters.     

Microscopic spin model for the stock market with attractor bubbling on scale-free networks

A multi-agent spin model for changes of prices in the stock market based on the Ising-like cellular automaton with interactions between traders randomly varying in time is investigated by means of Monte Carlo simulations. The structure of interactions has topology of scale-free networks with degree distributions obeying a power scaling law with various scaling exponents. The scale-free networks are obtained as growing networks where new nodes (agents) are linked to the existing ones according to a preferential attachment rule with an initial attractiveness ascribed to each node. In certain ranges of parameters, depending on the exponent in the degree distribution, the time series of the logarithmic price returns exhibit intermittent bursting typical of volatility clustering, and the tails of the distributions of returns obey a power scaling law with exponents comparable to those obtained from the empirical data. The distributions of returns show also dependence on the number of agents, in particular in the case of networks with the scaling exponents of the degree distributions typical of the social and communications networks.     

Collusion under monitoring of sales

Collusion under imperfect monitoring is explored when firms' prices are private information and their quantities are public information; such an information structure is consistent with several recent price‐fixing cartels, such as those in lysine and vitamins. For a class of symmetric oligopoly games, it is shown that symmetric equilibrium punishments cannot sustain any collusion. An asymmetric punishment is characterized that does sustain collusion and it has firms whose sales exceed their quotas compensating those firms with sales below their quotas. In practice, cartels could have performed such transfers through sales among the cartel members.     

On discounted dynamic programming with unbounded returns

In this paper, we apply the idea of k-local contraction of Rincón-Zapatero and Rodriguez-Palmero (Econometrica 71:1519–1555, 2003; Econ Theory 33:381–391, 2007) to study discounted stochastic dynamic programming models with unbounded returns. Our main results concern the existence of a unique solution to the Bellman equation and are applied to the theory of stochastic optimal growth. Also a discussion of some subtle issues concerning k-local and global contractions is included.     

The closedness of the free-disposal hull of a production set

Summary Assume thatL is a topological vector lattice andY is a closed subset ofL ₊ ×R ^N, whereR ^N denotes theN-dimensional Euclidean space. It is shown that the setY–L ₊ ×R ₊ ^N is closed ifY has appropriate monotonicity properties. The result is applicable to the case ofL equal toL with the Mackey topology, (L ,L ¹).