This paper addresses the question of how to model individual behavior in the face of changes in the set of rules that govern the social welfare system in Sweden. To this end, the Swedish sickness insurance provides an excellent study object, since the system has often been changed during the past decade. The question of employee compensation for sick leave is one the more widely discussed aspects of Swedish social welfare legislation, and it is therefore of interest to examine how individuals respond to changes in this legislation. We also examine how individual response to changes in the system can depend upon differences in socioeconomic and demographic characteristics. <br> Count data methods are used to estimate the econometric model. Preliminary results suggest that socioeconomic and demographic variables are important in explaining individuals reaction to the changes.