This work addresses the study of the evolution of employment between 2005 and 2018 in the Spanish economy using the theoretical framework of the Theoría de la Segmentación Laboral (TSL). First, atypical employment is quantified at 50 % of total membership, following a temporary drop caused mainly by the economic crisis, there is a strong boom, especially among young people. Secondly, it is noted that the instability of temporary contracts has increased as the average duration of contracts fell, which seems to be associated with the increase in contracts of very short duration (7 days or less). These changes are essentially explained by the fact that four professional subgroups, characteristic of the secondary segment, have a greater weight in the procurement structure. This can be attributed to increased turnover as a result of the labour-market “relaxation” policies introduced in the last decade.