Beyond unobserved heterogeneity in computer wage premiums / Data on computer use in Germany, 1997 – 2001

Beyond unobserved heterogeneity in computer wage premiums: Most findings on the (non-)existence of a wage premium on computer use are biased because they are based on single-equation estimation of a wage equation. Controlling for fixed effects ignores the simultaneity problem. Through the introduction of a latent variable, “PC-feasibility”, we tackle the problem of simultaneity and account for unobserved heterogeneity. Due to the simultaneous nature of wage determination and computer use, the premium for computer use becomes dependent on person and job characteristics. Imposing testable restrictions on the reduced form enables us to identify the factors that determine wages and enhance computer use. The model is estimated using German data, 1997-2001 Data on computer use in Germany, 1997 – 2001: This paper describes the GSOEP data, 1997-2001, used in Muysken and Schim van der Loeff (2006). The data contain relevant information on individuals, with a focus on the computer use both at home and at work. The construction of the relevant data set for the period 1997 - 2001 is presented in section 2. A more detailed discussion of the data is presented in section 3 for the 1997 wave. Interesting observations are that most workers who use a computer at work started to use a computer at home simultaneously or later. Also the average number of years of employment for workers exceeds the period of the sample. Moreover there is a huge amount of inertia for computer use at work. This emphasises that fixed effects do not only control for unobserved individual characteristics, but also firm and job related characteristics. Finally, for rather homogenous groups of workers wages do not appear to vary systematically with computer use.Cross-Sectional Models, Wage Differentials by Skill

On Bayesian and non-Bayesian estimation of a two-level CES production function for the Dutch manufacturing sector

In this paper maximum-likelihood estimates of the parameters of the two-level CES function, obtained by direct estimation of this function, are given. In addition the authors propose to show how a Bayesian analysis may help to find a solution to the difficulties related with, but not specific to, this particular estimation problem. It is shown that numerical integration of the posterior distribution may give an indication as to which parameter has to be pinpointed and at which value when multi-collinearity precludes unconditional maximization of the likelihood. It is suspected that this approach has a wider field of application

Persistence of Innovation in Dutch Manufacturing: Is it Spurious?

This paper studies the persistence of innovation and the dynamics of innovation output in Dutch manufacturing using firm data from three waves of the Community Innovation Surveys (CIS), pertaining to the periods 1994-1996, 1996-1998, and 1998-2000. We estimate by maximum likelihood a dynamic panel data type 2 tobit model accounting for individual effects and handling the initial conditions problem. We find that there is no evidence of true persistence in achieving technological product or process innovations, while past shares of innovative sales condition, albeit to a small extent, current shares of innovative sales. Cette étude analyse la persistance et la dynamique de l’innovation dans les entreprises manufacturières néerlandaises à partir des données de trois vagues d’enquêtes communautaires sur l’innovation (ECI), portant sur les périodes 1994-1996, 1996-1998 et 1998-2000. Nous estimons par la méthode du maximum de vraisemblance un modèle tobit de type II dynamique sur données de panel avec effets individuels et traitement explicite des conditions initiales. Nous concluons qu’il n’y a pas de véritable persistance dans le fait d’innover en produits ou en procédés, mais que les observations passées des parts du chiffre d’affaires en produits innovants influencent, quoique faiblement, les données contemporaines de ces parts.dynamic panel data type 2 tobit, innovation, spurious persistence, modèle tobit de type II dynamique, données de panel, persistence, innovation

The role of Zap70 in naïve T cell homeostasis

TCR signalling is crucial to both T cell development and naive T cell homeostasis. Naïve T cell survival in the periphery is thought to depend on both cytokine signalling and constitutive TCR signalling. The nature of this TCR dependent survival signal remains controversial. The tyrosine kinase, Zap70, is essential for TCR signalling. The aim of this project is to investigate the role of Zap70 in the transduction of survival signals in naïve T cells. Using mice that conditionally express Zap70 by means of a tetracycline-inducible system, we found that Zap70 is absolutely required for the maintenance of naïve T cells in the periphery. Loss of Zap70 resulted in a dramatic and rapid reduction in mature naive CD8 T cells in the blood and peripheral organs consistent with a naïve T cell survival defect. This survival defect could not be accounted for by cell-intrinsic differences in IL-7Rα or Bcl-2 expression. Analysis of T cell survival in vitro revealed no differences in responses to IL-7 between F5 T cells with or without Zap70. Survival in vitro was found to be enhanced by the presence of CD1 1 c+ enriched splenocytes but not T or B cells. Survival of F5 T cells in these cultures was dependent on Zap70 expression and also required intact MEK signalling. In addition, we also tested the ability of previously described Zap70 mutants, Zap70 SKG and Zap70YYAA, to transduce homeostatic TCR survival signals in vivo. Both mutants were unable to support the development, survival or antigen-induced expansion of F5 T cells. Additionally, we found evidence that Zap70Y YAA had a dominant negative effect on T cell development and reconstitution in F5 TetZap70 mice. In conclusion, we find that Zap70 is essential for transmission of signals required for naive T cell survival and requires both full expression and functionality of Zap70

The Behavior of the Maximum Likelihood Estimator of Dynamic Panel Data Sample Selection Models

This paper proposes a method to implement maximum likelihood estimation of the dynamic panel data type 2 and 3 tobit models. The likelihood function involves a two-dimensional indefinite integral evaluated using “two-step” Gauss-Hermite quadrature. A Monte Carlo study shows that the quadrature works well in finite sample for a number of evaluation points as small as two. Incorrectly ignoring the individual effects, or the dependence between the initial conditions and the individual effects results in an overestimation of the coefficients of the lagged dependent variables. An application to incremental and radical product innovations by Dutch business firms illustrates the method.

Persistence of Innovation in Dutch Manufacturing: Is it Spurious?

This paper studies the persistence of innovation and the dynamics of innovation output in Dutch manufacturing using firm data from three waves of the Community Innovation Surveys (CIS), pertaining to the periods 1994-1996, 1996-1998, and 1998-2000. We estimate by maximum likelihood a dynamic panel data type 2 tobit model accounting for individual effects and handling the initial conditions problem. We find that there is no evidence of true persistence in achieving technological product or process innovations, while past shares of innovative sales condition, albeit to a small extent, current shares of innovative sales.Economics ;

Innovative Sales, R&D and Total Innovation Expenditures: Panel Evidence on their Dynamics

This paper studies the dynamic relationship between input and output of innovation in Dutch manufacturing using an unbalanced panel of enterprise data from five waves of the Community Innovation Survey during 1994-2004. We estimate by maximum likelihood a dynamic panel data bivariate tobit with double-index sample selection accounting for individual effects. We find persistence of innovation input and innovation output, a lag effect of the former on the latter and a feedback effect of the latter on the former. The lag effect remains significant in the high-tech sector even after four years. Firm and industry effects are also important.innovation, panel bivariate tobit model, innovation expenditures

Financial Constraints and Other Obstacles: Are they a Threat to Innovation Activity?

In this paper we examine the importance of financial and other obstacles to innovation in the Netherlands using statistical information from the CIS 3.5 innovation survey. We report results on the effect of these obstacles on the firms' decision to abandon, prematurely stop, seriously slow down, or not to start an innovative project. These results are compared with those from other studies in the Netherlands and other countries. We end with a discussion of policy measures that have been taken to overcome, or at least attenuate these obstacles, such as R&D tax incentives, venture capital financing and policy mix pakages.Financial Constraints, Innovation, Innovation Policy