Prior symmetry, similarity-based reasoning, and endogenous categorization

This paper presents a rational theory of categorization and similarity-based reasoning. I study a model of sequential learning in which the decision maker infers unknown properties of an object from information about other objects. The decision maker may use the following heuristics: divide objects into categories with similar properties and predict that a member of a category has a property if some other member of this category has this property. The environment is symmetric: the decision maker has no reason to believe that the objects and properties are a priori different. In symmetric environments, categorization is an optimal solution to an inductive inference problem. Any optimal solution looks as if the decision maker categorizes. Various experimental observations about similarity-based reasoning coincide with the optimal behavior in my model.     

Selecting Your Inflation Targeters: Background and Performance of Monetary Policy Committee Members

Abstract. This paper starts by describing the composition of monetary policy committees (MPCs) in inflation‐targeting and non‐targeting countries. The experience of MPC members on their inflation performance is then compared, opposing inflation targeters with non‐targeters. Our sample covers the major Organization for Economic Cooperation and Development countries, in the period 1999–2008. Our results first show that MPCs are different in inflation‐targeting (versus non‐targeting) countries. They also reveal that policy‐makers' backgrounds influence inflation, and that the influence of MPCs' experience is much greater in inflation‐targeting countries, while size effects are more important for committees that do not target inflation.     

An evolutionary model of energy transitions with interactive innovation-selection dynamics

We develop a stylized application of a new evolutionary model to study an energy transition in electricity production. The framework describes a population of boundedly rational electricity producers who decide each period on the allocation of profits among different energy technologies. They tend to invest in below-average cost energy technologies, while also devoting a small fraction of profits to alternative technological options and research on recombinant innovation. Energy technologies are characterized by costs falling with cumulative investments. Without the latter, new technologies have no chance to become cost competitive. We study the conditions under which a new energy technology emerges and technologies coexist. In addition, we determine which investment heuristics are optimal in the sense of minimizing the total cost of electricity production. This is motivated by the idea that, while diversity contributes to system adaptability (innovation) and resilience to unforeseen contingencies (keeping options open), a high cost will discourage investments in it.     

Risk Diversification on the Polish Capital Market

The basics of portfolio management theory and methods of efficient selection of assets and their financing have been created by Markowitz and Sharpe. They propose that risk diversification consists, generally speaking, of the increase in the number of securities in a portfolio. So, authors try to answer the question of how many securities have to be bought on a given market to assure a well-diversified portfolio, where the increase in the number of securities does not lead to a significant decrease in portfolio risk. To evaluate such a purpose on the Polish capital market, 20 companies were surveyed that are included in the WIG20 index in the period January 2–October 10, 2001. The returns were estimated on a weekly basis. The research shows that a portfolio of securities constructed, according to the Sharpe Model, has a wide application to the Polish capital market.*University of Szczecin—Poland. This paper was presented at the Fifty-Eighth InternationalAtlantic Economic Conference, October 6Y9, 2005, Chicago, U.S.A.     

Dividend-Driven Trading Strategies: Evidence from the Warsaw Stock Exchange

This study presents an analysis of dividend-driven trading strategies based on dividend yield growth effects in the Polish stock market in the years 1994–2004. Results indicate that the dividend yield growth portfolios were capable of beating the market in the entire sample period. Their performance, however, was not consistent over time and the highest returns were obtained during final years. Empirical findings based on the analysis of different types of portfolios demonstrate the importance of dividends as a source of significant fundamental information items from stock market companies. At the same time, they show that a dividend investment strategy for the Polish stock market is most successful when the selection of stocks for the dividend yield growth portfolios is subject to further restrictions, most notably concerning company size.

Economic impact of contrast-induced acute kidney injury associated with invasive cardiology: role of iso-osmolar contrast media in Germany,Italy, Poland,and Spain

Objective:

Iso-osmolar Iodixanol is associated with a lower rate of contrast-induced acute kidney injury (CI-AKI) in patients at increased risk compared to low-osmolar contrast media (LOCM). The aim of this study was to assess the financial consequences of CI-AKI risk reduction in patients undergoing coronary angiography (CA) with or without percutaneous coronary intervention (PCI) in German, Italian, Polish and Spanish hospitals.

Methods:

This budget impact analysis (BIA) compared a scenario with iodixanol to a scenario without, where only LOCM were used, in patients at increased risk of CI-AKI over a 3-year horizon. A meta-analysis based on a systematic review observed a lower rate of CI-AKI with iodixanol compared to LOCM (Risk Reduction?=?0.46) in patients with underlying impaired renal function (serum creatinine ≥1.6?mg/dl and estimated glomerular filtration rate ≤50?ml/min/1.73 m²). Contrast media and CI-AKI hospitalization costs were included in the analysis and unit costs were obtained from published literature, official sources or, when available, from hospital data. In the absence of country-specific data, resource utilization for a CI-AKI hospitalization was obtained by interviews with local clinicians in each country. The percentage of patients who received iodixanol was assumed to increase over time.

Results:

Based on a percentage of patients at increased risk of CI-AKI equal to 20% in Germany, 24% in Italy, 23% in Poland and 10% in Spain, results showed that the introduction of iodixanol would bring a 3-years cumulative net percentage saving on the total hospital budget of 29%, 34%, 25%, and 33% in the four countries respectively.

Conclusion:

The results of the analysis for the four countries showed that iodixanol use in patients at increased risk of CI-AKI undergoing CA with or without PCI may bring considerable savings on the hospital’s budget, due to the associated reduction in CI-AKI incidence.     

Employability and the psychological contract in European ICT sector SMEs

This article explores the employability of information and communication technology (ICT) professionals from the perspective of small- and medium-sized enterprises (SMEs). The first stage of analysis, based on over 100 interviews with managers of ICT supplier companies in seven European countries (Germany, Greece, Italy, the Netherlands, Norway, Poland and the UK), showed most SMEs to have a generally ad hoc approach to managing the employability of their ICT professionals. Assessment and development plans were used primarily to keep skills current to business needs; however, the more developed northern European markets showed greater awareness of the ‘high commitment’ benefits of a more sophisticated approach towards career management (e.g. through mentoring or career planning). A second stage of analysis based only on UK interviews builds on this to propose a model of positive employer influence on psychological contracts through career and employability management practices.     

Popularity of reinforcement-based and belief-based learning models: An evolutionary approach

In an evolutionary model, players from a given population meet randomly in pairs each instant to play a coordination game. At each instant, the learning model used is determined via some replicator dynamics that respects payoff fitness. We allow for two such models: a belief-based best-response model that uses a costly predictor, and a costless reinforcement-based one. This generates dynamics over the choice of learning models and the consequent choices of endogenous variables. We report conditions under which the long run outcomes are efficient (or inefficient) and they support the exclusive use of either of the models (or their co-existence).     

The Satellite Insurance Market and Underwriting Cycles

This research analyses whether underwriting cycles are present in an important but often overlooked line of insurance, satellite insurance. Unlike previous underwriting cycle studies, this study uses rates-on-line and capacity devoted to satellite insurance as well as loss ratios to determine the applicability of cycles. The sample period encompasses virtually the entire history of the satellite insurance industry, 1968–2010. The results indicate that cycles are present in the minimum and average rates-on-line and in capacity, but not the loss ratio. Regression analysis is carried out on the rate-on-line and capacity variables, and the regression results support the rational expectations/institutional intervention hypothesis and the capacity constraint (capital shock) hypothesis.     

Analysis of a network structure of the foreign currency exchange market

We analyse structure of the world foreign currency exchange (FX) market viewed as a network of interacting currencies. We analyse daily time series of FX data for a set of 63 currencies, including gold, silver and platinum. We group together all the exchange rates with a common base currency and study each group separately. By applying the methods of filtered correlation matrix we identify clusters of closely related currencies. The clusters are formed typically according to the economical and geographical factors. We also study topology of weighted minimal spanning trees for different network representations (i.e., for different base currencies) and find that in a majority of representations the network has a hierarchical scale-free structure. In addition, we analyse the temporal evolution of the network and detect that its structure is not stable over time. A medium-term trend can be identified which affects the USD node by decreasing its centrality. Our analysis shows also an increasing role of euro in the world’s currency market.