THE IDENTITY OF THE ZERO-TRUNCATED, ONE-INFLATED LIKELIHOOD AND THE ZERO-ONE-TRUNCATED LIKELIHOOD FOR GENERAL COUNT DENSITIES WITH AN APPLICATION TO DRINK-DRIVING IN BRITAIN

For zero-truncated count data, as they typically arise in capture-recapture modelling, we consider modelling under one-inflation. This is motivated by police data on drink-driving in Britain which shows high one-inflation. The data, which are used here, are from the years 2011 to 2015 and are based on DR10 endorsements. We show that inference for an arbitrary count density with one-inflation can be equivalently based upon the associated zero-one truncated count density. This simplifies inference considerably including maximum likelihood estimation and likelihood ratio testing. For the drink-driving application, we use the geometric distribution which shows a good fit. We estimate the total drink-driving as about 2,300,000 drink-drivers in the observational period. As 227,578 were observed, this means that only about 10% of the drink-driving population is observed with a bootstrap confidence interval of 9%-12%.