Regression models for bivariate count outcomes

We present a new command, bivcnto, for fitting regression models suitable for analyzing correlated count outcomes. bivcnto allows specification of two correlated count outcomes with either two outcome-specific covariate lists or one common covariate list and fits models using a copula function approach in the general case or using specific parameterizations by Marshall and Olkin (1985, Journal of the American Statistical Association 80: 332–338) or Famoye (2010a, Journal of Applied Statistics 37: 969–981; 2010b, Statistica Neerlandica 64: 112– 124). bivcnto also calculates a likelihood-ratio test comparing the joint model with estimation of two independent outcome-specific models.