Germany experienced a unique rise in the level of self-employment in the first two decades following unification. Applying the non-linear Blinder-Oaxaca decomposition technique, we find that the main factors driving these changes in the overall level of self-employment are demographic developments, the shift towards service sector employment, and a larger share of population holding a tertiary degree. While these factors explain most of the development in self-employment with employees and the overall level of self-employment in West Germany, their explanatory power is much lower for the stronger increase of solo self-employment and of self-employment in former socialist East Germany.