[Market Concentration in the Statutory Health Insurance of Germany since the Introduction of Free Choice of Sickness Funds].

The expansion of trust law to the German statutory health insurance (SHI) and the declining numbers of sickness funds suggest a strong concentration process in the German SHI market. The paper examines the level and development of market concentration since the introduction of the free choice of sickness funds in 1996. The study is based on a dataset containing information on membership, contribution rate, openness, area of activity and legal successor for all sickness funds in the period from 1996 to 2013. Market concentration is measured by the concentration rate (cumulative market share of the largest market participants) and the Herfindahl-Hirschman index (HHI). In addition, the change in the HHI is also disaggregated into 3 factors: opening, switching and fusion of sickness funds. Concentration rate and HHI decreased significantly between 1996 and 2008 due to opening of former closed sickness funds and a switching behaviour from large to small funds. The SHI Competition Enhancement Act of 2007 led to a turnaround. The reform permitted cross-type mergers and introduced a completely new system of budget allocation with the central health fund. The latter put an end to the growing membership of small funds due to adverse selection processes. As a result, market concentration in the German SHI rises. Although recent mega-mergers were uncritical for nationwide competition, the study already indicates the risk of market dominance on the regional level.