Excess Zeros in Count Models for Recreational Trips.

This article develops a modeling approach for a count data set for recreational boating trips that shows a frequency of zero counts significantly higher than that expected for Poisson distributed data. As alternatives to the Poisson regression, the authors consider several parametric and semiparametric mixed and modified Poisson models. The analysis suggests that the negative binomial hurdles model, which allows for overdispersion and also accommodates the presence of 'excess zeros,' is the most satisfactory of all those considered.