Testing Models With Multiple Equilibria by Quantile Methods

This paper proposes a method for testing complementarities between explanatory and dependent variables in a large class of economic models. The proposed test is based on the monotone comparative statics (MCS) property of equilibria. Our main result is that MCS produces testable implications on the (small and large) quantiles of the dependent variable, despite the presence of multiple equilibria. The key features of our approach are that (i) we work with a nonparametric structural model of a continuous dependent variable in which the unobservable is allowed to be correlated with the explanatory variable in a reasonably general way; (ii) we do not require the structural function to be known or estimable; (iii) we remain fairly agnostic on how an equilibrium is selected. We illustrate the usefulness of our result for policy evaluation within Berry, Levinsohn, and Pakes's (1999) model.     

Market Structure and Multiple Equilibria in Airline Markets

We provide a practical method to estimate the payoff functions of players in complete information, static, discrete games. With respect to the empirical literature on entry games originated by Bresnahan and Reiss (1990) and Berry (1992), the main novelty of our framework is to allow for general forms of heterogeneity across players without making equilibrium selection assumptions. We allow the effects that the entry of each individual airline has on the profits of its competitors, its “competitive effects,” to differ across airlines. The identified features of the model are sets of parameters (partial identification) such that the choice probabilities predicted by the econometric model are consistent with the empirical choice probabilities estimated from the data. We apply this methodology to investigate the empirical importance of firm heterogeneity as a determinant of market structure in the U.S. airline industry. We find evidence of heterogeneity across airlines in their profit functions. The competitive effects of large airlines (American, Delta, United) are different from those of low cost carriers and Southwest. Also, the competitive effect of an airline is increasing in its airport presence, which is an important measure of observable heterogeneity in the airline industry. Then we develop a policy experiment to estimate the effect of repealing the Wright Amendment on competition in markets out of the Dallas airports. We find that repealing the Wright Amendment would increase the number of markets served out of Dallas Love.     

Ideology and the Affective Structure of Whites' Racial Perceptions

The present study tests the hypothesis that deviations from"affective bipolarity" in the relationship between the positiveand negative dimensions of whites’ stereotypes of blacks—suchas racial ambivalence—should be stronger among conservatives.Across two different data sets (the 2000 National Election Studyand the 1991 National Race and Politics Study) and three differentmethodologies (heteroskedastic regression, confirmatory factoranalysis, and a regression analysis of attitude-ambivalencescores), this hypothesis was supported. Further analyses indicatedthat the relationship between conservatism and ambivalent perceptionsof blacks was mediated by conflict between humanitarian andindividualistic concerns in the racial context, but not in theabstract.     

Bootstrap Inference in Partially Identified Models Defined by Moment Inequalities: Coverage of the Identified Set

This paper introduces a novel bootstrap procedure to perform inference in a wide class of partially identified econometric models. We consider econometric models defined by finitely many weak moment inequalities, ² We can also admit models defined by moment equalities by combining pairs of weak moment inequalities.
which encompass many applications of economic interest. The objective of our inferential procedure is to cover the identified set with a prespecified probability. ³ We deal with the objective of covering each element of the identified set with a prespecified probability in Bugni (2010a).
We compare our bootstrap procedure, a competing asymptotic approximation, and subsampling procedures in terms of the rate at which they achieve the desired coverage level, also known as the error in the coverage probability. Under certain conditions, we show that our bootstrap procedure and the asymptotic approximation have the same order of error in the coverage probability, which is smaller than that obtained by using subsampling. This implies that inference based on our bootstrap and asymptotic approximation should eventually be more precise than inference based on subsampling. A Monte Carlo study confirms this finding in a small sample simulation.     

Inequality in voting power

This paper deals with the assessment of inequality in the distribution of voting power. Voting power is evaluated through a general concept of power measurement based on both the voting rule and the probability distribution over vote configurations. This general concept includes as particular cases the most usual power indices and other extensions of this traditional concept. Thus no particular power index is privileged in our approach. An inequality index over the class of all power profiles with a given number of voters generated by this general measure is then singled out by requiring reasonable properties. In order to compare profiles with different numbers of voters, two alternative principles are considered, which extend the said index consistently in two ways.Previous versions of this work were circulated under different titles. We gratefully acknowledge financial support from the Spanish Ministerio de Ciencia y Tecnología under the Ramón y Cajal programme and under projects PB96-0247 and BEC2000-0875; from the European Commission under the Training and Mobility of Researchers programme (contract FMRX - CT966-0055); and from the Instituto Valenciano de Investigaciones Económicas. We also thank two anonymous referees for their comments.2 October 2001     

Internationalisation and outsourcing of operations and product development in the fashion industry

This paper investigates the choices in terms of internationalisation and outsourcing of operations and product development activities, as well as collaboration practices used within and across organisations, in different segments of the European fashion industry. Based on multiple, in-depth case studies from Italy, Germany and the UK, the paper shows that fashion companies adopt different configurations of operations and product development, i.e. integrated, collaborative and virtual, ranging from local-integrated models to global-full outsourcing of operations and product development activities. For each configuration, different collaboration practices are in use. Product line positioning and quality, firm size, sales volumes and technical complexity of the products are the key drivers determining the configuration choices and the adoption of certain collaboration practices.     

The Impact of Privatization on the Earnings of Restructured Workers: Evidence From the Oil Industry

We study the long-term impact of job displacement from a big state owned enterprise as a result of its privatization in a developing country. Our results suggest large reductions in earnings, which persist throughout the years. However, we also find that the displaced worker’s post-displacement earnings are in line with competitive market wages, and unrelated to sector of employment or to tenure losses, indicating that the long-term reduction in earnings as a result of displacement because of privatization can be traced to the loss of wage rents. Our results indicate that job displacement in SOEs may have very large redistributive implications for the workers involved but that this loss does not necessarily reflect the loss of specific human capital associated to these jobs.

Fully Nonparametric Estimation of Scalar Diffusion Models

We propose a functional estimation procedure for homogeneous stochastic differential equations based on a discrete sample of observations and with minimal requirements on the data generating process. We show how to identify the drift and diffusion function in situations where one or the other function is considered a nuisance parameter. The asymptotic behavior of the estimators is examined as the observation frequency increases and as the time span lengthens. We prove almost sure consistency and weak convergence to mixtures of normal laws, where the mixing variates depend on the chronological local time of the underlying diffusion process, that is the random time spent by the process in the vicinity of a generic spatial point. The estimation method and asymptotic results apply to both stationary and nonstationary recurrent processes.     

A consistent and numerically efficient variable selection method for sparse Poisson regression with applications to learning and signal recovery

Statistics and Computing - We propose an adaptive $$\ell _1$$ -penalized estimator in the framework of Generalized Linear Models with identity-link and Poisson data, by taking advantage of a...     

Examining the Incidence and Clients’ Experiences of Single Session Therapy in Italy: A Feasibility Study

Single session therapy (SST) postulates that one session can be sufficient for a client to take charge of the process and work toward their own solutions. Research has been conducted worldwide corroborating SST assumptions with several mental health conditions, but not in Italy. For the first time in Italy, this paper aims to explore: (1) if the most frequent number of sessions in traditional psychotherapy (not SST) is one (Study 1); and (2) the satisfaction of clients who attend SST services and the number who consider one session sufficient to address their presenting problem (Study 2). In Study 1, the records of 476 voluntary clients referred to three different traditional (not SST) psychological services in the west-central region of Latium, Italy, were retrospectively screened, and the number of sessions attended by each client recorded. In Study 2, 85 consecutive clients who voluntarily asked for SST with seven mental health professionals across Italy received a link to an online ad hoc survey, 1–3 weeks after the consultation, evaluating their experience. Study 1 found that the most frequent number of traditional psychotherapeutic (not intentionally SST) sessions was one (124 out of 476 clients (26%). Study 2 found that 44 out of 85 clients (52%) considered one session to be enough, as they felt better or much better and chose not to attend further sessions. Of those who asked for a second session (41 clients), 33 clients (80.5%) indicated that the first session was not enough and 8 clients (19.5%) wanted to address a new problem. These results converge with previous international studies and provide encouragement for the use of SST in both private and public psychological services to address the demand for timely mental health services in Italy. Further research is needed to support the efficacy of SST and to evaluate its cost-effectiveness.