The current system to elect the German Bundestag (i.e. German Federal Parliament) has a major defect: more votes for one party can lead to less seats in the parliament for that same party - the so called negative voting weight. The German Federal Constitution Court has requested the Parliament to modify the electoral system in order to avoid this malfunction. There are lots of possible solutions to that problem. In this paper we attempt to evaluate several possible modifications from a Social Choice perspective. We introduce a simple system of conditions for electoral systems by which we classify possible modifications. It follows that there cannot exist an electoral system that satisfies all of these conditions. There are solutions, however, which satisfy more conditions than other possible modifications.