Sveinn Vidar Gudmundsson
In this chapter concentration in the US air transport market is assessed by calculating the Herfindahl–Hirschman Index separately for the domestic and the international market. The findings show that industry concentration in the US domestic market fluctuates substantially, usually increasing in the years following recessions and receding during periods of economic prosperity. In the international market US airlines have strengthened their position compared to international airlines, judging from a rising Herfindahl–Hirschman Index. Overall, the oligopolistic characteristics of the domestic market are stronger than in the international market, yet neither market shows strong concentration characteristics using the US Department of Justice criteria.