Sulla nozione di riassunto esaustivo

Si studiano dal punto di vista formale (ponendosi in un quadro astratto molto generale) le relazioni tra la nozione di riassunto esaustivo «in senso classico» e quella di riassunto esaustivo «in senso bayesiano». In particolare si analizzano, per ciascuna di queste nozioni, le condizioni di validità della fattorizzazione di Neyman.

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Résumé On étudie d'un point de vue purement formel (en se plaçant dans un cadre abstrait très général) les relations entre la notion de résumé exhaustif «au sens classique» et celle de résumé exhaustif «au sens bayesien».On analyse notamment, pour chacune de ces deux notions, les conditions de validité de la factorisation de Neyman.

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Pubblichiamo volentieri questo articolo di G. Letta, che per l'impostazione astratta si allontana alquanto dall'ambito degli interessi scientifici di questa Rivista, perché l'argomento trattato è strettamente legato ad un lavoro di D. M. Cifarelli ed E. Regazzini recentemente comparso sul nostro periodico (vedi [3] e la 2^a parte in questo fascicolo).     

Is Social Security Really Bad for Growth?

This paper develops a model of endogenous growth with overlapping generations to investigate the joint determination of social security, public investment, and growth in a small open economy. We show that a pure pay-as-you-go system with benefits indexed to wages provides taxpayers with incentives to support growth-oriented policies, which increase the future productivity of labor. We find that outcomes characterized by positive levels of intergenerational redistribution, public investment, and long-run growth can be sustained as subgame-perfect Nash equilibria of an infinitely repeated intergenerational game, if and only if the marginal productivity of public capital is large enough. Furthermore, we show that transfers comove with public investment and growth. Journal of Economic Literature Classification Numbers: E62, H55.     

ON THE HIERARCHY OF SOME QUALITATIVE STRUCTURES IN THE VON NEUMANN AND RELATED MODELS

In this paper we collect some old and new qualitative-structural properties on the input and output matrices involved in the classical von Neumann model, properties relevant, from the formal and/or economic point of view, in the study of the equilibria of the said model. It is established the hierarchy, i.e. the relations of inclusion, partial overlapping and disjunction, among these properties, which permits to amend some current slips in the analysis of the von Neumann model (one due to von Neumann himself). The results obtained can be fitted to other production and exchange multisectorial models.     

Can Hedge Funds Time the Market?

We answer the somewhat narrower question of whether hedge funds adjust their conditional market exposure in response to real‐time changes in macroeconomic conditions, and whether doing so improves their performance. We find that hedge funds differ substantially in their responsiveness to macroeconomic data. The most procyclical market timers outperform their less active and counter‐cyclical peers by over 4% annualized with a risk adjusted alpha of 5.5%.     

Effects of the Adoption of IFRS on the Credit Market: Evidence from Brazil

Based on a sample of approximately 6500 credit ratings and 137,000 loan contracts, this paper analyzes the effects of mandatory IFRS adoption on the Brazilian credit market. We find that the IFRS adoption effects were limited to firms displaying improved accounting information quality at the time of transition, lending support to the notion that economic benefits do not necessarily flow from the publication of financial reports in IFRS but, rather, depend on how earnestly firms adopt the recommended disclosure practices.     

A dynamic exchange rate model with heterogeneous agents

In this paper, we analyze a heterogeneous agent model in which the fundamental exchange rate is endogenously determined by the real markets. The exchange rate market and the real markets are linked through the balance of payments. We have analytically found that there exists at least a steady state in which the exchange rate is equal to its fundamental value and incomes of both countries are equal to the autonomous components times the multiplier (as in the Income-Expenditure model). This steady state can be unique and unstable when all agents act as contrarians, while when agents act as fundamentalists it is unique but its stability depends on the reactivity of actors of the market. Finally, we show that the (in)stability of the economic system depends on both the reactivity of the markets and that of different types of agents involved. Employing well-know functional forms, we show that the model can replicate some of the statistical features of the true time series of the exchange rate.     

The international-trade network: gravity equations and topological properties

This paper begins to explore the determinants of the topological properties of the international-trade network (ITN). We fit bilateral-trade flows using a standard gravity equation to build a “residual” ITN where trade-link weights are depurated from geographical distance, size, border effects, trade agreements, and so on. We then compare the topological properties of the original and residual ITNs. We find that the residual ITN displays, unlike the original one, marked signatures of a complex system, and is characterized by a very different topological architecture. Whereas the original ITN is geographically clustered and organized around a few large-sized hubs, the residual ITN displays many small-sized but trade-oriented countries that, independently of their geographical position, either play the role of local hubs or attract large and rich countries in relatively complex trade-interaction patterns.     

The effect of a law limiting upcoding on hospital admissions: evidence from Italy

Policy makers have made several attempts to limit hospitals’ upcoding. We investigate the impact of a law introducing a minimum length of stay for discharges with complications. We analyze its effects on the probability of a discharge with complications, on its length of stay and on its reimbursement. We show that the policy has been effective in limiting upcoding, since, after the law, (1) the probability of a discharge with complications has decreased by 3%; (2) its length of stay has risen by 0.17 days more than the observed corresponding variation in the length of stay of a discharge in the control group; (3) the hospital’s revenue on a discharge with complications has decreased by 8.5% more than the observed revenue change on a discharge in the control group. Furthermore, we find evidence of an ownership effect on upcoding, since not-for-profit and for-profit hospitals have been more affected by the law than public hospitals.