Electoral System Design: The New International IDEA Handbook  

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. However, while conscious design has become far more prevalent recently, traditionally it has been rare for electoral systems to be consciously and deliberately selected. Often the choice was essentially accidental, the result of an unusual combination of circumstances, of a passing trend, or of a quirk of history, with the impact of colonialism and the effects of influential neighbours often being especially strong.