305,525 research outputs found
Unobservable factors and panel data sets: an investigation in the labour market
No full textThis paper investigates the effects of unobservable factors that, as is well-known, contaminate two of the variables most used in labour market research, namely the stock of unemployment and the stock of vacancies. Using a matching function framework, we compare different panel data estimators using a number of appropriate Hausman tests robust to deviations from the classical errors assumptions. The relevance of the choice of the model specification is underlined. It is shown to what extent conclusions lacking a rigorous statistical analysis may be misleading
On the estimation of covariance matrices using panel data artificial regressions
No full textThe use of artificial regressions to compute the variance of the difference of pairs of panel data estimators that cannot be ranked in terms of efficiency is considered. It is illustrated how it is possible to get (asymtotically) valid estimators of covariance matrices for differences between estimators when the assumption that the error term in the auxiliary model is IID is violated. We distinguish two possible deviations, one leading only to a non-spherical-within groups covariance matrix and the second leading to a non-spherical-between-groups covariance matrix also. It is shown to what extent the use of an artificial regression with panel data can lead to a robust estimator of the covariance matrix in the first case whereas it leads to a non valid estimator in the second. An alternative step by step procedure is presented
Testing the exogeneity assumption in panel data models with "non classical" disturbances
No full textThis paper is concerned with the use of the Durbin-Wu-Hausman test for correlated effects with panel data. The assumptions underlying the construction of the statistic are too strong in many empirical cases. The consequences of deviations from the basic assumptions are investigated. The size distortion is assessed. In the case of measurement error, the Hausman test is found to be a test of the difference in asymptotic biases of between and within group estimators. However, its 'size' is sensitive to the relative magnitude of the intra-group and inter-group variations of the covariates, and can be so large as to preclude the use of the statistic in this case. We show to what extent some assumptions can be relaxed in a panel data context and we discuss an alternative robust formulation of the test. Power considerations are presented
Geography and economic performance: exploratory spatial data analysis for Great Britain
No full textThis paper uses the techniques of exploratory spatial data analysis to examine patterns of spatial association for different indicators of economic performance and in so doing identifies and describes the spatial structure of economic performance in Great Britain
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Influencing connected legislators
No full textThis paper studies how interest groups allocate campaign contributions when congressmen are connected by social ties. We establish conditions for the existence of a unique Nash equilibrium in pure strategies for the contribution game and characterize the associated allocation of the interest groups’ moneys. While the allocations are generally complex functions of the environment (the voting function, the legislators’ preferences, and the social network topology), they are simple, monotonically increasing functions of the respective legislators’ Katz-Bonacich centralities. Using data on the 109th–113th Congresses and on congressmen’s alumni connections, we estimate themodel and find evidence supporting its predictions
Forces on a spherical conducting particle in E x B fields
No full textThe forces acting on a spherical conducting particle in a transversely flowing magnetized plasma are calculated in the entire range of magnetization and Debye length, using the particle code SCEPTIC3D (Patacchini and Hutchinson 2010 Plasma Phys. Control. Fusion 52 035005, 2011 Plasma Phys. Control. Fusion 53 025005). In short Debye length (i.e. high density) plasmas, both the ion-drag and Lorentz force arising from currents circulating inside the dust show strong components antiparallel to the convective electric field, suggesting that a free dust particle should gyrate faster than what predicted by its Larmor frequency. In intermediate to large Debye length conditions, by a downstream depletion effect already reported in unmagnetized strongly collisional regimes, the ion-drag in the direction of transverse flow can become negative. The internal Lorentz force, however, remains in the flow direction, and large enough in magnitude so that no spontaneous dust motion should occur.National Science Foundation (U.S.)United States. Dept. of Energy (grant DE-FG02-06ER54891
Latent Variables in Panel Data Models: Theoretical Contributions and Empirical Applications
No full textThis book addresses statistical issues related to linear panel data models with the joint occurrence of unobserved heterogeneity and measurement errors- in-variables. Specifically, it is concerned with hypothesis testing and estimation techniques in a static and in a dynamic framework respectively. The relevance of such issues for applied studies is emphasized. Different case-studies are analyzed
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