International differences in wage inequality remain a reality, despite efforts of negotiations and demands of the unions and contrary to the will of international organizations and associations for an international minimum wage. At the same time, the fall in wages and, specifically in minimum wages, combined with the decline of unionization are facts that seem connected.
This article presents the results of a quantitative research-using the Mann-Whitney non-parametric test and the linear bivariate correlation-which examines the potential connection between the Gross Domestic Product and union density in 33 member-states of the OECD, while examining the type of the correlation between them. The research results showed that high Gross Domestic Product is directlyproportional to the size of union density and that there is a positive correlation between the two.