Among the 31 countries using an open-list system, there are considerable differences. Seven countries use a one-preference systemwhereas 24 countries use a system with several preferences, either a fixed or a variable number of preferences. Among these 24 countries, seven countries use a fixed number of preferences; ten countries use a system of several preferences; Liechtenstein, Luxembourg, Monaco and Switzerland use cross-voting (also called panachage) whereas Sweden uses the system of adjustment seats (also called apparentements); finally, Ireland and Malta use a single-transferable-vote system.