Private versus public financing of education and endogenous growth

This paper examines interactions between education policy and growth. The analysis is carried out in an OLG model with two types of individuals: skilled and unskilled. An increase in public education reduces private costs of education, increases the proportion of skilled individuals, and tends to promote growth. On the other hand, education spending crowds out physical capital and reduces learning-by-doing. A marginal increase in the education subsidy can lower growth. It is yet shown that pure public education maximizes the long-run growth rate. Importantly, a partial subsidy to education can result in lower growth than pure private education. Received: 7 March 1999/Accepted: 25 November 1999     

Detecting change in a hazard regression model with right-censoring

The hazard function plays an important role in survival analysis and reliability, since it quantifies the instantaneous failure rate of an individual at a given time point t, given that this individual has not failed before t. In some applications, abrupt changes in the hazard function are observed, and it is of interest to detect the location of such a change. In this paper, we consider testing of existence of a change in the parameters of an exponential regression model, based on a sample of right-censored survival times and the corresponding covariates. Likelihood ratio type tests are proposed and non-asymptotic bounds for the type II error probability are obtained. When the tests lead to acceptance of a change, estimators for the location of the change are proposed. Non-asymptotic upper bounds of the underestimation and overestimation probabilities are obtained. A short simulation study illustrates these results.     

Optimal designs based on exact confidence regions for parameter estimation of a nonlinear regression model

This paper is concerned with the proposal of optimality criteria, referred to as X  - and X^′$X^{\prime }$-optimality criteria, and the construction of X  - and X^′$X^{\prime }$-optimal designs, for nonlinear regression models. These optimal designs aim at improving the estimation of parameters of this class of models. The principle of these criteria is the minimization, with respect to the design, of the expected volume of a particular exact parametric confidence region. In this paper we give detailed definitions, properties, and computation methods of X  - and X^′$X^{\prime }$-optimal designs. We also compare these designs with the classic local D-optimal designs, with regard to robustness and efficiency, for two very well-known academic models (Box–Lucas and Michaelis–Menten models).     

Joint Modeling of Event Time and Nonignorable Missing Longitudinal Data

Survival studies usually collect on each participant, both duration until some terminal event and repeated measures of a time-dependent covariate. Such a covariate is referred to as an internal time-dependent covariate. Usually, some subjects drop out of the study before occurence of the terminal event of interest. One may then wish to evaluate the relationship between time to dropout and the internal covariate. The Cox model is a standard framework for that purpose. Here, we address this problem in situations where the value of the covariate at dropout is unobserved. We suggest a joint model which combines a first-order Markov model for the longitudinaly measured covariate with a time-dependent Cox model for the dropout process. We consider maximum likelihood estimation in this model and show how estimation can be carried out via the EM-algorithm. We state that the suggested joint model may have applications in the context of longitudinal data with nonignorable dropout. Indeed, it can be viewed as generalizing Diggle and Kenward's model (1994) to situations where dropout may occur at any point in time and may be censored. Hence we apply both models and compare their results on a data set concerning longitudinal measurements among patients in a cancer clinical trial.     

Mutualism in the world: Ignorance, inequalities and market pressures

Anyone engaged on research who tries to get to know, evaluate and describe the mutual benefit movement in its worldwide context always comes up against the differences in terminology and in constitutions, as well as the disparate nature and unreliability of the financial statements: an international maze in which the observer is completely lost. In spite of the real efforts of the Association internationale de la mutualité (International Association of Mutual Benefit Societies — AIM), the European Community, the International Social Security Association (ISSA), the Institute of International Social Cooperation (ICOSI) and of universities, the history, assessment and evolution — both recent and comparative — of the mutual benefit movement remain largely "terra incognita".     

Scoring reversals: a major league dilemma

Recent work shows that, in theory scoring methods are very sensitive to the scoring points used. I analyze the results of Most Valuable Player voting in baseball as a test of the practical relevance of this work. I find that Most Valuable Player rankings are indeed quite dependent on the particular scoring points in use.The author thanks Bill Deane of the National Baseball Hall of Fame for supplying voting data, and Gary Cohen and Andy Schotter for discussions. Technical support from the G. V. Storr Center for Applied Economics is gratefully acknowledged.     

The Uses of Observation in French Sociology

Until quite recently, questionnaire surveys, semi-structured interviews and the gathering and interpreting of various documents have been the main kinds of empirical research to be found in French sociology. Observation plays a leading role in none of them, even in the latter. The researchers who use it do not seem convinced of its legitimacy, because what can be expected from systematic observation does not fit the prevailing purpose of developing abstract, general theories. After having sketched out the institutional and intellectual background, this paper examines a few examples of French studies using observation. Most of them fail to clearly distinguish between indirect evidence and direct observation, between meaning as construed by the observer and that experienced by the people observed; they rarely report dated and situated facts (even more seldom behaviors than settings), and they replace the expected analyses of these missing facts with the interpretation of would-be typical or usual facts.     

Effects of sleep inertia on cognitive performance following a 1-hour nap

This study investigated the effects of a 1-h nap on subsequent performance in spatial memory (SM) and logical reasoning (LR) tasks. The objective was to evaluate the duration of the effects of sleep inertia (SI). The performance was measured in two independent groups of subjects. The 1-h nap took place at 00:00 h in group 1 and at 03:00 h in group 2. In each task, the experimental design comprised one no-nap condition in which subjects had no sleep before the night tests, and a nap condition that comprised the 1-h nap followed by the test sessions. To measure the duration of SI effects, the subjects were tested in two 30-min sessions and the data in each session were analysed in sub-units of time of 3 min each. In each task the results showed no effects on accuracy, and no circadian effects of napping were found. In each task, analyses of pooled data of the two groups showed that the performance in the 1-h nap condition exhibited significant reductions of speed immediately following awakening, when compared with no-nap, reflecting SI effects. In SM, the slowing lasted 24 min, and 27 min in LR. Practical implications of the results are discussed.