Testing for monotone increasing hazard rate

A test of the null hypothesis that a hazard rate is monotone nondecreasing, versus the alternative that it is not, is proposed. Both the test statistic and the means of calibrating it are new. Unlike previous approaches, neither is based on the assumption that the null distribution is exponential. Instead, empirical information is used to effectively identify and eliminate from further consideration parts of the line where the hazard rate is clearly increasing; and to confine subsequent attention only to those parts that remain. This produces a test with greater apparent power, without the excessive conservatism of exponential-based tests. Our approach to calibration borrows from ideas used in certain tests for unimodality of a density, in that a bandwidth is increased until a distribution with the desired properties is obtained. However, the test statistic does not involve any smoothing, and is, in fact, based directly on an assessment of convexity of the distribution function, using the conventional empirical distribution. The test is shown to have optimal power properties in difficult cases, where it is called upon to detect a small departure, in the form of a bump, from monotonicity. More general theoretical properties of the test and its numerical performance are explored.Comment: Published at http://dx.doi.org/10.1214/009053605000000039 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

How Effective are Fiscal Incentives for R&D? A New Review of the Evidence

This paper surveys the econometric evidence on the effectiveness of fiscal incentives for R&D. We describe the effects of tax systems in OECD countries on the user cost of R&D - the current position, changes over time and across different firms in different countries. We describe and criticize the methodologies used to evaluate the effect of the tax system on R&D behavior and the results from different studies. In the current (imperfect) state of knowledge we conclude that a dollar in tax credit for R&D stimulates a dollar of additional R&D.

Can Pay Regulation Kill? Panel Data Evidence on the Effect of Labor Markets on Hospital Performance

Labor market regulation can have harmful unintended consequences. In many markets, especially for public sector workers, pay is regulated to be the same for individuals across heterogeneous geographical labor markets. We would predict that this will mean labor supply problems and potential falls in the quality of service provision in areas with stronger labor markets. In this paper we exploit panel data from the population of English acute hospitals where pay for medical staff is almost flat across the country. We predict that areas with higher outside wages should suffer from problems of recruiting, retaining and motivating high quality workers and this should harm hospital performance. We construct hospital-level panel data on both quality - as measured by death rates (within hospital deaths within thirty days of emergency admission for acute myocardial infarction, AMI) - and productivity. We present evidence that stronger local labor markets significantly worsen hospital outcomes in terms of quality and productivity. A 10% increase in the outside wage is associated with a 4% to 8% increase in AMI death rates. We find that an important part of this effect operates through hospitals in high outside wage areas having to rely more on temporary "agency staff" as they are unable to increase (regulated) wages in order to attract permanent employees. By contrast, we find no systematic role for an effect of outside wages of performance when we run placebo experiments in 42 other service sectors (including nursing homes) where pay is unregulated.labor market regulation, hospital quality, hospital productivity, skills

A novel synthesis of 2'-hydroxy-1',3'-xylyl crown ethers

Six novel 2' - hydroxy - 1',3' - xylyl crown ethers (8a–e and 13)1 have been synthesized utilizing the allyl group to protect the OH function during the cyclization reaction. The macrocycles 6a-e were formed in yields of 26 to 52%, by intermolecular reaction of 4 - chloro - 2,6 - bis(bromomethyl) - 1 - (2 - propenyloxy)benzene (5) with polyethylene glycols; 6a was also obtained by an intramolecular cyclization reaction of monotosylate 14.\ud A 30-membered ring with a 2' - hydroxy - 1',3' - xylyl sub-unit was obtained in 87% yield by reaction of ditosylate 9 with bis [2 - (o - hydroxyphenoxy)ethyl]ether (11) in the presence of cesium fluoride. The synthesis of crown ethers with a 2' - hydroxy - 1',3' - xylyl sub-unit (1c–e, H for CH3) by demethylation of the corresponding 2'-methoxy crown ethers 1c–e with lithium iodide were unsuccessful; it would appear that the demethylation reaction is restricted to 15- and 18-membered rings. One of the 2' - hydroxy - 1',3' - xylyl crown ethers 8d forms a crystalline 1:1-complex with water

Measuring capital flight : a case study of Mexico

The authors show how the various methods commonly used to measure capital flight produce vastly different estimates (with a 100 percent difference between the lowest and the highest, in Mexico's case). They emphasize the importance of the conceptual approach to its measurement. First of all, they did not try to separate normal capital flows from capital flight. A capital shift outward because of expected taxation is as much a response to anticipated developments in rate of return as is a shift out in response to lower interest rates at home. Nor is it satisfactory to directly measure capital flight by taking short-term asset changes and the balance of errors and omissions from the balance of payments. Neither is necessarily related to the unreported private accumulation of foreign assets. They chose the residual approach, which assumes that capital inflows in the form of increases in external indebtedness and foreign direct investment should finance either the current account or reserve accumulation; any shortfall in reported use can be attributed to capital flight. Implementing the residual approach requires careful data selection and several adjustments. The authors contend that: introducing debt stock data into the analysis - instead of the changes in debt recorded directly in the balance of payments - requires many difficult adjustments and should be avoided; foreign asset changes of public corporations must be subtracted; rather than eliminate interest received on foreign assets from the current account, as some have done, earnings on private assets held abroad should be considered part of the flight capital that might have been repatriated, given different incentives and macroeconomic conditions; and the effect on capital flight of the faking of trade invoices should be assessed, since import overinvoicing and export underinvoicing can be used to channel capital abroad. They demonstrate the empirical importance of these choices with a new set of capital flight estimates for Mexico, based on the recommendations they present. They contrast the results of this approach with those of other approaches, to demonstrate the effect of conceptual choices.Environmental Economics&Policies,Economic Theory&Research,Banks&Banking Reform,International Terrorism&Counterterrorism,Settlement of Investment Disputes

Resampling-based confidence regions and multiple tests for a correlated random vector

We derive non-asymptotic confidence regions for the mean of a random vector whose coordinates have an unknown dependence structure. The random vector is supposed to be either Gaussian or to have a symmetric bounded distribution, and we observe $n$ i.i.d copies of it. The confidence regions are built using a data-dependent threshold based on a weighted bootstrap procedure. We consider two approaches, the first based on a concentration approach and the second on a direct boostrapped quantile approach. The first one allows to deal with a very large class of resampling weights while our results for the second are restricted to Rademacher weights. However, the second method seems more accurate in practice. Our results are motivated by multiple testing problems, and we show on simulations that our procedures are better than the Bonferroni procedure (union bound) as soon as the observed vector has sufficiently correlated coordinates.Comment: submitted to COL