Do Institutions, Ownership, Exporting and Competition Explain Firm Performance? Evidence from 26 Transition Countries

We analyze a large stratified random sample of firms that provide us with measures of performance and each firm’s top manager’s perception of the severity of business environment constraints faced by his/her firm. Unlike most existing studies that rely on external and aggregated proxy measures of the business environment, defined to include legal and institutional features, we have information from each surveyed firm. Specifically, we use the 2005 and 2002 Business Environment and Enterprise Performance Survey (BEEPS) to assess the effect on performance of ownership, competition, export orientation and the business environment of the firm. We employ a variety of approaches to deal with the problem of omitted variables, errors in variables and endogeneity that plague studies in this area. We find that foreign ownership and competition have an impact on performance – measured as the level of sales controlling for inputs. Export orientation of the firm does not have an effect on performance once ownership is taken into account. When we analyze the impact of perceived constraints, we show that few retain explanatory power once they are introduced jointly rather than one at a time, or when country, industry and year fixed effects are introduced. Indeed, country fixed effects largely absorb the explanatory power of the constraints faced by individual firms. Replicating the analysis with commonly used country-level indicators of the business environment, we do not find much of a relationship between constraints and performance. Our analysis brings into question an important part of the conventional wisdom in this area. It indicates that country fixed effects, reflecting time-invariant differences in the business environment but also other factors, matter for firm performance, but that differences in the business environment observed across firms within countries do not. Moreover, the limited firm and country-level variations in the business environment over time do not appear to affect performance either. This suggests that the effect of business environment on performance and the analysts’ ability to identify this effect are more limited than has been assumed to date.firm performance, productivity, competition, institutions, business environment, export orientation, firm ownership, subjective data

Stiffness of finite free resolutions and the Canonical Element Conjecture

Over a noetherian local ring certain minimal finite free resolutions possess a property which we call stiffness. This calls to mind the Buchsbaum-Eisenbud criterion for exactness. Yet we only prove stiffness over equicharacteristic rings. However, Hochster's Canonical Element Conjecture is shown to be true for every ring with a fixed prime residual characteristic, precisely when every resolution over each Gorenstein ring of this type is stiff.Comment: 11 page

Infinite products of finite simple groups

We classify those sequences $\langle S_{n} \mid n \in \mathbb{N} \rangle$ of finite simple nonabelian groups such that the full product $\prod_{n} S_{n}$ has property (FA).Comment: AMS-LaTex file, 44 pages. To appear in Tran. Amer. Math. So

Detection and localization of change points in temporal networks with the aid of stochastic block models

A framework based on generalized hierarchical random graphs (GHRGs) for the detection of change points in the structure of temporal networks has recently been developed by Peel and Clauset [1]. We build on this methodology and extend it to also include the versatile stochastic block models (SBMs) as a parametric family for reconstructing the empirical networks. We use five different techniques for change point detection on prototypical temporal networks, including empirical and synthetic ones. We find that none of the considered methods can consistently outperform the others when it comes to detecting and locating the expected change points in empirical temporal networks. With respect to the precision and the recall of the results of the change points, we find that the method based on a degree-corrected SBM has better recall properties than other dedicated methods, especially for sparse networks and smaller sliding time window widths.Comment: This is an author-created, un-copyedited version of an article accepted for publication/published in Journal of Statistical Mechanics: Theory and Experiment. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/1742-5468/2016/11/11330

Visceral leishmaniasis in eastern Africa--current status.

Visceral leishmaniasis (VL) is among the most neglected of the tropical diseases, afflicting the poorest of the poor. In eastern Africa, VL causes at least 4000 deaths annually, a loss of approximately 385,000 disability-adjusted life years. Due to the chronicity of underlying causes, it is likely that the caseload will increase in the foreseeable future. While efforts should be pursued to develop novel case management and prevention tools, several effective interventions already exist but are rarely deployed. Funds are needed now to procure commodities and strengthen health systems, so that effective VL control can be delivered to populations at risk

Creating conditions of anomalous self-diffusion in a liquid with molecular dynamics

We propose a computational method to simulate anomalous self-diffusion in a simple liquid. The method is based on a molecular dynamics simulation on which we impose the following two conditions: firstly, the inter-particle interaction is described by a soft-core potential and secondly, the system is forced out of equilibrium. The latter can be achieved by subjecting the system to changes in the length scale at intermittent times. In many respects, our simulation system bears resemblance to slowly driven sandpile models displaying self-organised criticality. We find non-Gaussian single time step displacement distributions during the out-of-equilibrium time periods of the simulation.Comment: Extended version: 12 pages, 9 figure

An easy computable upper bound for the price of an arithmetic Asian option.

Using some results from risk theory on stop-loss order and comonotone risks, we show in this paper that the price of an arithmetic Asian option can be bounded from above by the price of a portfolio of European call options.