AbstractThe Dutch healthcare insurance reform in 2006 replaced the dual system of public and private insurance with a single compulsory health insurance scheme, in which insurance providers compete for customers in a free market. This paper investigates whether competition among healthcare insurers has indeed increased and their efficiency has improved. We measure competition directly from either shifts in market shares, or developments in profits, using Dutch regulatory data. We find that a structural break occurs after the reform: competition is significantly higher after 2006 than before. This holds both for the analysis based on shifts in market shares and that based on profits. Several robustness tests confirm this outcome. Hence, the reform has had a significant impact. Nevertheless, we find that the health insurance sector is still less competitive than financial sectors such as banking and life insurance.