TY  - JOUR
A1  - Slama, R.
A1  - Werwatz, A.
T1  - Controlling for continuous confounding factors : non- and semiparametric approaches
N2  - Confounding is one of the major types of bias encountered in observational epidemiologic surveys designed to study the relation between an exposure factor and a health event. A common way to remove confounding bias during the statistical analysis phase is to adjust for the confounders in a regression model. If a confounding factor is assessed as a continuous variable, it is necessary to define how the variable is entered into the regression model. In the case of logistic regression, we illustrate through simulation that coding by a binary variable or a categorical variable with broad categories may lead to substantial residual confounding. Specific approaches can be used to define a coding method that limits residual confounding. Among these, we briefly present nonparametric approaches and describe in detail several semiparametric approaches (generalised partial linear models, spline regression and fractional polynomials). These can be used to estimate the relation between a continuous factor and the health event of interest by a smooth non pre-specified function. In semiparametric models, the effect of certain covariates is coded by a parametric function, whereas the coding of one or two continuous variables is represented by a nonparametric function. These models can be used in exploratory analyses to describe dose-effect relations between the confounder and the health event, and thus help to define a relevant coding for the confounder
Y1  - 2005
SN  - 0398-7620
ER  - 
TY  - JOUR
A1  - Gorzig, B
A1  - Gornig, M
A1  - Werwatz, A
T1  - Explaining eastern Germany's wage gap : the impact of structural change
N2  - Since Eastern Germany's conversion to a market economy wages have remained considerably below the West German wage level. This article looks at the role of establishment-specific factors-such as sectoral affiliation and size of the labour force-in this process. A non-parametric decomposition that has played a prominent role in the gender wage gap literature is applied to breakdown the East-West wage gap into its constituent components. Using establishment data from German employment statistics, the article demonstrates that the catching-up process of Eastern Germany's wage level is hindered by the shift in its economic structure towards lower-paying types of companies, which has caused the lagging behind in the adjustment of wages
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Christensen, B. J.
A1  - Lentz, R.
A1  - Mortensen, D. T.
A1  - Neumann, G. R.
A1  - Werwatz, A.
T1  - On-the-job search and the wage distribution
N2  - The article structually estimates an on-the-job search model of job separations. Given each employer pays observably equivalent workers the same but wages are dispersed across employers, an employer's separation flow is the sum of an exogenous outflow unrelated to the wage and a job-to-job flow that decreases with the employer's wage. Using data from the Danish Integrated Database for Labour Market Research, the empirical results imply, as predicted by theory, that search effort declines with the wage. Furthermore, the estimates explain the employment effect, defined as the horizontal difference between the distribution of wages earned and the wage offer distribution
Y1  - 2005
SN  - 0734-306X
ER  -