A New Bivariate Regression Model for Count Data with Excess Zeros

Count data often display excessive number of zero outcomes compared to what is expected in Poisson regression. Zero-inflated Poisson (ZIP) regression has been suggested to handle purely zero-inflated data, whereas zero-inflated generalized Poisson regression model has been fitted for zero-inflated data with additional overdispersion. For bivariate and zero-inflated data, several regression models such as bivariate zero-inflated generalized Poisson (BZIGP) have been considered. This paper introduces a new form of BZIGP. The main advantages of such new form of BZIGP regression are that it has flexible form of mean-variance relationship, it can be fitted to bivariate zero-inflated count data with positive, zero or negative correlations, and it allows additional overdispersion of the two dependent variables.