Comparable Worth: Blind spots in the analysis of the gender pay gap

As a rule, the earnings in women-dominated occupations are significantly lower than in male-dominated occupations. The research project Comparable Worth investigated the extent to which discrimination in job evaluation on the basis of gender is concealed behind this. The project was the first to statistically determine the extent to which unequal pay for work of comparable worth is currently paid on the German labour market and the extent to which this results in income disadvantages, especially for women. In purely legal terms, equal pay must be paid not only for the same work, but also for work of equal value in German companies or within the scope of a collective agreement.

The research questions arose against the theoretical background of the "Comparable Worth" approach, which, inspired in particular by gender sociology, assumes that female gainful employment is systematically undervalued by gendered and discriminatory job valuations. Previously, this approach had not been extensively statistically tested. Empirically, undervaluations of female gainful employment have so far only been proven in individual cases. It was unclear if and to what extent they were relevant for the gender pay gap as a whole. The project attempted to close this research gap.

Two project modules based on each other were worked on.

As part of the first module, a Comparable Worth Index was constructed on the basis of the BIBB/BAuA survey of employed persons, which makes it possible to identify activities of equal value from an occupational science point of view and in accordance with legal standards. To create the index, various aspects of the job were taken into account, such as psychosocial requirements or demands on knowledge and skills. The index was then validated using both quantitative and qualitative methods.

Building on the results of the first project module, the second module provided for further multivariate analyses based on the German earnings structure survey. For this purpose, the "Comparable Worth Index" was fed into the data of the Structure of Earnings Survey. Among other things, a "Comparable Worth Gap" was calculated, which quantifies the extent to which the earnings of women and men who perform equivalent tasks from the point of view of work science differ.

The aim of the project was to contribute to the analysis of the causes of the gender pay gap and, in particular, to investigate the share of job evaluation in the pay gap.

The project results confirm the devaluation hypothesis. Overall, a gender pay gap of around 10% could be determined when controlling for work requirements and personal characteristics. The gap between men's and women's wages increases with increasing workload (increasing CW value). Collective agreements are able to mitigate this difference between women's and men's wages for comparable job requirements, but they do not eliminate it.