In a large sample of Swedish unemployed disabled workers, the workers participate in between zero and ten policy programmes during their unemployment spell. Clustering of programmes to about half of the sample is prominent. <p> The number of programmes is modelled as a standard count data model, as...</p>

Applications of zero-inflated count data models have proliferated in empirical economic research. There is a downside to this development, as zero-inflated Poisson or zero-inflated Negative Binomial Maximum Likelihood estimators are not robust to misspecification. In contrast, simple Poisson...