Colombia introduced a market-determined Nominal Exchange Rate (NER) with the US Dollar in 1991, after more than 20 years of controlled and multiple exchange rates. The first nine years the NER was set by an exchange rate band system, since 1999 the exchange rate is determined in a dirty float"...

Developing sound or reliable statistical models for analyzing vehicle crashes is veryimportant in highway safety studies. A difficulty arises when crash data exhibit overdispersion.Over-dispersion caused by unobserved heterogeneity is a serious problemand has been addressed in a variety ways...