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We investigate methods and tools for analysing translations between programming languages with respect to observational semantics. The behaviour of programs is observed in terms of may- and must-convergence in arbitrary contexts, and adequacy of translations, i.e., the reflection of program equivalence, is taken to be the fundamental correctness condition. For compositional translations we propose a notion of convergence equivalence as a means for proving adequacy. This technique avoids explicit reasoning about contexts, and is able to deal with the subtle role of typing in implementations of language extension.
The paper proposes a variation of simulation for checking and proving contextual equivalence in a non-deterministic call-by-need lambda-calculus with constructors, case, seq, and a letrec with cyclic dependencies. It also proposes a novel method to prove its correctness. The calculus' semantics is based on a small-step rewrite semantics and on may-convergence. The cyclic nature of letrec bindings, as well as non-determinism, makes known approaches to prove that simulation implies contextual equivalence, such as Howe's proof technique, inapplicable in this setting. The basic technique for the simulation as well as the correctness proof is called pre-evaluation, which computes a set of answers for every closed expression. If simulation succeeds in finite computation depth, then it is guaranteed to show contextual preorder of expressions.
We develop a multivariate generalization of the Markov–switching GARCH model introduced by Haas, Mittnik, and Paolella (2004b) and derive its fourth–moment structure. An application to international stock markets illustrates the relevance of accounting for volatility regimes from both a statistical and economic perspective, including out–of–sample portfolio selection and computation of Value–at–Risk.
An asymmetric multivariate generalization of the recently proposed class of normal mixture GARCH models is developed. Issues of parametrization and estimation are discussed. Conditions for covariance stationarity and the existence of the fourth moment are derived, and expressions for the dynamic correlation structure of the process are provided. In an application to stock market returns, it is shown that the disaggregation of the conditional (co)variance process generated by the model provides substantial intuition. Moreover, the model exhibits a strong performance in calculating out–of–sample Value–at–Risk measures.
This paper documents and studies sources of international differences in participation and holdings in stocks, private businesses, and homes among households aged 50+ in the US, England, and eleven continental European countries, using new internationally comparable, household-level data. With greater integration of asset and labor markets and policies, households of given characteristics should be holding more similar portfolios for old age. We decompose observed differences across the Atlantic, within the US, and within Europe into those arising from differences: a) in the distribution of characteristics and b) in the influence of given characteristics. We find that US households are generally more likely to own these assets than their European counterparts. However, European asset owners tend to hold smaller real, PPP-adjusted amounts in stocks and larger in private businesses and primary residence than US owners at comparable points in the distribution of holdings, even controlling for differences in configuration of characteristics. Differences in characteristics often play minimal or no role. Differences in market conditions are much more pronounced among European countries than among US regions, suggesting significant potential for further integration.
Marginal income taxes may have an insurance effect by decreasing the effective fluctuations of after-tax individual income. By compressing the idiosyncratic component o personal income fluctuations, higher marginal taxes should be negatively correlated with the dispersion of consumption across households, a necessary implication of an insurance effect of taxation. Our study empirically examines this negative correlation, exploiting the ample variation of state taxes across US states. We show that taxes are negatively correlated with the consumption dispersion of the within-state distribution of non-durable consumption and that this correlation is robust.
Based on a unique dataset of legislative changes in industrial countries, we identify events that strengthen the competition control of mergers and acquisitions, analyze their impact on banks and non-financial firms and explain the different reactions observed with specific regulatory characteristics of the banking sector. Covering nineteen countries for the period 1987 to 2004, we find that more competition-oriented merger control increases the stock prices of banks and decreases the stock prices of non-financial firms. Bank targets become more profitable and larger, while those of non-financial firms remain mostly unaffected. A major determinant of the positive bank returns is the degree of opaqueness that characterizes the institutional setup for supervisory bank merger reviews. The legal design of the supervisory control of bank mergers may therefore have important implications for real activity.
Sachsen war mit seinen guten Ergebnissen in der Ländervergleichsstudie PISA 2003 die große Überraschung, - weniger unter den ostdeutschen Ländern; da hatte auch Thüringen und Sachsen-Anhalt gut abgeschnitten gegenüber PISA 2000. Sachsen stellte auch die in der ersten Studie erfolgreichen westdeutsche Länder Bayern und Baden-Württemberg in den Schatten. Auf die Frage nach den Gründen kam man sehr rasch zu der Vermutung, die guten Ergebnisse könnten etwas mit der Struktur des sächsischen Schulsystems zu tun haben. Das Land hatte, wie auch Sachsen-Anhalt und Thüringen, für kurze Zeit nach der Wende ein dreigliedriges System und hat seitdem neben dem Gymnasium nur noch eine Mittelschule, in der Haupt- und Realschule vereinigt sind. In die Mittelschule gingen 2003 61,3 Prozent der Schüler/innen, ins Gymnasium 32 Prozent. Seit der Veröffentlichung des zweiten PISA-Ländervergleichs wird darum die nicht ganz neue Frage heftiger diskutiert, ob nicht schon eine Reduktion der Schulformen von vier oder drei auf zwei uns im internationalen Leistungsvergleich voranbringen könnte und zugleich die vor allem westdeutschen Probleme mit der rapide schwindenden Akzeptanz der Hauptschule beseitigen würde. Was in dieser Diskussion bislang kaum ins Blickfeld geriet: Sachsen ist zweigliedrig nur bis Ende Klasse 6 und bis dahin muss in der Mittelschule entschieden und für Eltern begründet sein, wer sich in separaten Klassen auf den Hauptschulabschluss und wer sich auf den Mittleren Abschluss vorbereiten kann. Der Unterschied zum traditionell dreigliedrigen System besteht also in der zeitlich gestaffelten Auslese nach Klasse 4 in Mittelschule und Gymnasium und nach Klasse 6 in "abschlussbezogene" Haupt- und Realschulklassen. Das war übrigens bis vor einigen Jahren auch das bayrische Schulsystem. Jetzt beginnt in Bayern die Realschule, wie im dreigliedrigen System sonst üblich, auch bereits mit Klasse 5. (Merkelbach 2007, S.2 f.) ...