Testing time-homogeneity of rating transitions after origination of debt

When modelling rating transitions as continuous-time Markov processes, in practice, time-homogeneity is a common assumption, yet restrictive, in order to reduce the complexity of the model. This paper investigates whether rating transition probabilities change after the origination of debt. Accordingly, we develop a likelihood-ratio test for the hypothesis of time-homogeneity. The alternative is a step function of transition intensities. The test rejects time-homogeneity for rating transitions observed over 7 years in a real corporate portfolio. Especially 1-year transition probabilities increase over the first year after origination. This time effect suggests that banks should manage their credit portfolios with respect to the age of debt.      

The Italian airport industry in transition: a performance analysis

This paper analyzes the impacts of Italian government actions on the efficiency of 36 airports between 2001 and 2003. The changes have included privatization, enlargement of the services provided directly by airport management companies, through the modification of the concession agreements, and the creation of two hubs. The analysis, using the consolidated two-stage data envelopment analysis with bootstrapping, indicates that airports with a majority public holding are on average more efficient and the presence of two hubs is source of inefficiency.