The project is supposed to significantly contribute to closing the scientific gap concerning the economic impacts of information technology (IT). These are still being discussed controversially, even though IT has been used in business for more than 50 years. IT has become on of the modern core technologies and its economic effects must also be searched for beyond the boundaries of traditional productivity analyses. The distinctive characteristics of IT are so far not adequately taken into consideration in theoretical and empirical analyses. Those results that treated IT as an aggregate are going to be expanded by differentiating IT in respect to its different fields of technology and their network effects. By evaluating the company databases existing at the ZEW, e.g. the Mannheimer Dienstleistungspanel and IT-Surveys, extensive insights into the impacts of IT on the productivity of companies in Germany will be gained. New stylized facts will facilitate the creation of theoretical models. There are three main goals: To improve the process of theoretical modelling and the empirical knowledge base concerning the use of IT in German companies. To discover whether the theoretical concept of general purpose technologies can be applied to IT and which implications this bears for analysing the economic consequences of IT-usage, with particular emphasis being placed on the connection between IT-usage and innovation processes. Finally to analyse, both theoretically and empirically, the impact of IT-usage on the development of productivity in the respective companies.