Ce serait plutôt les intérims à très court terme si on parle d'une entreprise.
Mais ça peut être aussi les emploi mal rémunérés (< 400€ / mois en Allemagne)

"An insignificant employment or activity in the sense of § 8 Abs. 1 Nr. 1 SGB IV, § 8a SGB IV exists, when the specified payment limit of Euro 400 per month regularly is not exceeded.
As insignificant are also considered the so-called short-term employments according to § 8 Abs. 1 Nr. 2 SGB IV, which are limited by their nature or in advance contractually limited to no more than two months or 50 working days within a calendar year. In such employments it is irrelevant how high the monthly salary is. Earnings from short-term employments are non-contributory in the statutory pension insurance; thus these employments can not be reported in the respective insurance accounts in the statistics on those actively insured because of missing data storage.
For recipients of a full pension because of old age, who practise an insignificant employment, for which according to § 172 Abs. 1 SGB VI exclusively employer contributions are paid, there is also no storage of insignificant periods of employment in the respective insurance account; they are included in the case group of recipients of pensions without contribution payments. "
http://www.gbe-bund.de/gbe10/abrechnung.prc_abr_test_logon?p...

"... que le nombre d'heures prestées par les intérimaires constitue un indicateur de grande valeur pour prédire l'évolution de l'emploi à très court terme. ..."
http://books.google.com/books?isbn=9020963589..