How does competition in the container liner shipping industry evolve over time? To answer this question, the present paper examines a new model-based measure of competition. This measure of competition based on Boone’s theoretical work quantifies the impact of marginal costs on performance, measured in terms of profits or market shares. Boone (2000 and 2004) shows that when profit differences are increasingly determined by marginal cost differences, this indicates increased competition. The evolution of competition will be calculated using a pooled data set of 20 liner operators. The analysis is carried out at industry level. After correcting for industry-specific effects (i.e. number of services, average ship size), the findings suggest that over the 2000-2008 period the competition has intensified. In addition, the paper also focuses on the relation between the Boone indicator and the Herfindahl-Hirschman Index. For policy makers, this research is especially relevant since no study has put forward the overall picture on the degree of competition at container division level.