The choice of electoral system is one of the most important institutional decisions for any democracy. In almost all cases the choice of a particular electoral system has a profound effect on the future political life of the country concerned, and electoral systems, once chosen, often remain fairly constant as political interests solidify around and respond to the incentives presented by them. The choices that are made may have consequences that were unforeseen as well as predicted effects.

Electoral system choice is a fundamentally political process, rather than a question to which independent technical experts can produce a single ‘correct answer’. The consideration of political advantage is almost always a factor in the choice of electoral systems. Calculations of short-term political interest can often obscure the longer-term consequences of a particular electoral system.

The choice of electoral system can have a significant impact on the wider political and institutional framework: it is important not to see electoral systems in isolation. Their design and effects are heavily contingent upon other structures within and outside the constitution. Successful electoral system design comes from looking at the framework of political institutions as a whole: changing one part of this framework is likely to cause adjustments in the way other institutions within it work.

Electoral systems are today viewed as one of the most influential of all political institutions, and of crucial importance to broader issues of governance. For example, it is increasingly being recognized that an electoral system can be designed both to provide local geographic representation and to promote proportionality; can promote the development of strong and viable national political parties, and ensure the representation of women and regional minorities; and can help to ‘engineer’ cooperation and accommodation in a divided society by the creative use of particular incentives and constraints.