Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
This paper deals with statistical methods for modelling individual behavior when the endogenous variable is a nonnegative integer. Examples are the number of children, the number of job changes or the number of shopping trips in a given period. Several approaches--Poisson, robust Poisson, negative binomial (NEGBIN), NEGBIN[subscript k], hurdle Poisson, truncated-at-zero Poisson--are discussed with a focus on specification, estimation, and testing. An application to labor mobility data illustrates the gain obtained by carefully taking into account the specific structure of the data. Copyright 1995 by Blackwell Publishers Ltd