Airport Concentration and Market Power: An Events Study Approach

This paper presents independent confirmation of the results obtained in recent studies that suggest mergers and acquisitions creating airline dominance at the airport level lead to market power. Using a different methodology – an events study for the 1986 merger of Northwest Orient Airlines and Republic Airlines – this paper confirms those results, indicating that concentration in the context of the sunk costs associated with the operation at a particular airport facility allows market power in the airline industry.     

Update on coronary artery calcium imaging

This update of coronary calcium imaging discusses methods of detecting and measuring coronary artery calcium and their correlation to coronary artery disease risk. The value of EBCT to traditional non-invasive cardiovascular tests is compared. A negative EBCT test makes the presence of atherosclerotic plaque, including unstable plaque, very unlikely. Negative EBCT may be consistent with low risk of a cardiovascular event over the next 2-5 years. Conversely, positive EBCT confirms the presence of a coronary plaque. The greater the amount of calcium, the greater the likelihood of occlusive disease, but there is a not a 1:1 relationship and findings may not be site specific. A high calcium score may be consistent with moderate to high risk of cardiovascular event within the next 2-5 years. Limitations and cautions concerning the general use of EBCT for screening are discussed.