Aim of the paper is to analyse the differences in survival times of job contracts among subgroups of workers, based on different socio-demographic characteristics such as age, gender, educational level, geographical area.

We examine the differences both in the length of the first job contract and in the waiting time between the end of the first contract and the beginning of a new one.

We in particular also the well-known Gini index to the measurement of concentration in survival times within groups of workers, and as a way to compare the distribution of survival times across such groups. We consider a test for differences in the heterogeneity of survival distributions, which may suggest the presence of a differential covariates effect on the job contract survival.

The analysis is based on the Italian Compulsory Communications system data, which record all the activations, transformations, fixed-term extensions and anticipated terminations of employment relationships between any worker and employer in Italy.