It's not so much "atypical contributions" as contributions paid by atypical workers.

June 2000 saw the first elections for workers' representatives on the administrative board of the social insurance fund for 1.8 million "atypical" consultancy and freelance workers, managed by Italy's National Institute for Social Insurance (Inps). The main trade union confederations received most of the votes, but the turn-out was very low.
The social insurance fund for "atypical" workers managed by Italy's National Institute for Social Insurance (Istituto nazionale di previdenza sociale, Inps) was created in 1995 by law 335, in order to guarantee social insurance coverage for such workers. The fund manages the contributions in respect of all atypical workers having an employment relationship "midway between" dependent employment and self-employment, such as consultancy and freelance work "coordinated" by an employer (collaborazione coordinata e continuativa). This type of employment contract regulates the professional services provided by workers who carry out their work on the basis of the directions and control of an undertaking, but whose presence in the company is not necessary and whose work does not imply a stable relationship with the company.

http://www.eiro.eurofound.eu.int/2000/08/inbrief/it0008160n....