On the estimation of the influence curve

We prove the asymptotic validity of bootstrap confidence bands for the influence curve from its usual estimator (the sensitive curve). The proof is based on the use of Gill's (1989) generalized delta method for Hadamard differentiable operators. The scope and applicability of this result are also discussed

Coordinates and frames from the causal point of view

Lorentzian frames may belong to one of the 199 causal classes. Of these numerous causal classes, people are essentially aware only of two of them. Nevertheless, other causal classes are present in some well-known solutions, or present a strong interest in the physical construction of coordinate systems. Here we show the unusual causal classes to which belong so familiar coordinate systems as those of Lema{\^{\i}}tre, those of Eddington-Finkelstein, or those of Bondi-Sachs. Also the causal classes associated to the Coll light coordinates (four congruences of real geodetic null lines) and to the Coll positioning systems (light signals broadcasted by four clocks) are analyzed. The role that these results play in the comprehension and classification of relativistic coordinate systems is emphasized.Comment: 5 pages, 1 figure, short communication in A Century of Relativity Physics, Proceedings of the XXVIII Spanish Relativity Meeting ERE-2006, 6-10 September - Oviedo - Spain (AIP Conference Proceedings

On robustness properties of bootstrap approximations

Bootstrap approximations to the sampling distribution can be seen as generalized statistics taking values in a space of probability measures. We first analyze qualitative robustness [in Hampel's (1971) sense] of these statistics when the initial estimators {Tn } (whose distributions we want to approximate using bootstrap resampling) are obtained by restriction from a statistical functional T defined for all probability distributions. Whereas continuity of T turns out to be the natural condition to ensure qualitative robustness of {Tn }, we show that the uniform continuity of T is a sufficient condition for robustness of the bootstrap. This result applies to M-estimators. Next, we study asymptotic properties of the bootstrap estimator for the infiuence function T'(F; x) of T at a distribution F and we prove that continuous Hadamard differentiability of the operator F_ T'(F;.) with respect to F is a natural condition to establish the validity of bootstrap confidence bands for this estimator

Tourism expenditure of EU-27 regions under the global economic crisis

This study focuses on the underpinnings of the households’ tourism expenditure decisions during the global economic crisis in 2009. In particular, this study tests if during an economic crisis, decisions on tourism expenditure depend on climate conditions of the place of origin, GDP and GDP growth, among other well-known determinants. It should be noted that cutback decisions on tourism expenditure are not independent of destination choice, and for that reason the model requires the estimation of both decisions simultaneously. The methodology proposed in this paper represents a new way of analyzing the impacts of an economic crisis on tourism expenditure. Two levels of analysis can be considered. On the one hand, macroeconomic data of tourism expenditure is usually explored. On the other hand, the microeconomic analysis of the household and regional variables of their environment that may enrich the analysis. If the econometric model takes into account all these variables simultaneously, then the linkage between GDP changes and tourists´ behavior is enriched and it may be estimated more accurately. As far as we know, this paper is the first study that models the cutback decision on tourism expenditure. Modeling such decision is a challenge because it is not independent of the destination choice. For instance, households that travel domestically may not be as sensitive to the crisis as those who travel abroad. For this purpose, the econometric model employed is a simultaneous system of cutback decision and destination choice. More precisely, Simultaneous Semi-Ordered Bivariate Probit has proved to be the most useful econometric model for the estimation because it deals with the simultaneity of the cutback and destination choice decisions as well as the endogeneity. This research has proved that during an economic crisis, households react cutting back their tourism expenditure depending on GDP, GDP growth, and climate in their place of origin. In that sense, there are marked differences between North-European and Mediterranean regions. It is interesting to note that regions with bad climate are less likely to cut back than those households located in regions with good climate.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Ultrastructure of adhesion and movement of the tetraspores of Gelidium Lamour (Geldiaceae; Rhodophyta)

The outer part of the tetraspora cell wall in Gelidium crinale (Turner) J.V. Lamour. and G. spathulatum (Kutz.) Bornet is morphologically described in relation to the movements and displacement of these spores when they settle on a substratum. We also describe the mechanism of adhesión and the transformations undergone by this mechanism over time. The cell wall shows a network of fibrillar threads embedded in abundant mucilage. The deformations that tetraspores undergo show that the cell wall is relatively elastic

Supervised classification for a family of Gaussian functional models

In the framework of supervised classification (discrimination) for functional data, it is shown that the optimal classification rule can be explicitly obtained for a class of Gaussian processes with "triangular" covariance functions. This explicit knowledge has two practical consequences. First, the consistency of the well-known nearest neighbors classifier (which is not guaranteed in the problems with functional data) is established for the indicated class of processes. Second, and more important, parametric and nonparametric plug-in classifiers can be obtained by estimating the unknown elements in the optimal rule. The performance of these new plug-in classifiers is checked, with positive results, through a simulation study and a real data example.Comment: 30 pages, 6 figures, 2 table

Tilting Rightward: C-SPAN's Coverage of Think Tanks

This study's main finding is that C-SPAN coverage of think tanks overwhelmingly favors conservative think tanks while left-of-center think tanks are under-represented. In 2006, conservative think tanks received 43.76 percent of total think tank coverage. Conservative/ libertarian and centrist think tanks received 6.94 percent and 31.76 percent respectively. Center-left and progressive think tanks, on the other hand, only received 12.73 percent and 4.86 percent respectively. Thus, the combined conservative and conservative/libertarian think tanks got an absolute majority of 50.7 percent representation on C-SPAN. Everything left of center got only 17.59 percent, just one third of the coverage received by the Right

Capital Controls and Monetary Policy in Developing Countries

This paper looks at both the theoretical and empirical literature on capital controls and finds that capital controls can play an important role in developing countries by helping to insulate them from some of the harmful effects of volatile and short-term capital flows. The authors look at controls on capitalinflows in Malaysia (1989-1995); Colombia (1993-1998); Chile (1989-1998); and Brazil (1992-1998), and also consider the case of Malaysia’s controls on outflows in 1998-2001. They conclude that there is sufficient backing in both economic theory and empirical evidence to consider more widespread adoption of capital controls in order to address some of the macroeconomic problems associated with short-term capital flows, to enable certain development strategies, and to allow policy makers more flexibility with regard to crucial monetary and exchange rate policies.capital controls, capital flows

The IMF and Economic Recovery: Is Fund Policy Contributing to Downside Risks?

The IMF's most recent World Economic Outlook (WEO), published last week, projects world economic growth will slow, from 4.8 percent in 2010 to 4.2 percent next year. Throughout the report, there are numerous concerns expressed about the "fragility" of the global economic recovery. The Acting Chair of the Executive Board states that "[t]he recovery is losing momentum temporarily during the second half of 2010 and will likely remain weak in the first half of 2011, as extraordinary policy stimulus is gradually withdrawn."In view of the report and its findings, one might expect a strong bias towards continuing fiscal stimulus in weak economies, and a bias against fiscal consolidation. However, this paper finds that the IMF continues to support pro-cyclical policies in some countries, fiscal consolidation in many others, and clearly does not support central bank financing of fiscal stimulus -- even in countries such as the United States -- where the threat of high inflation is very remote