Can the Electoral Threshold Explain – some part of – Electoral Volatility in Belgium?

Recent election results showed an increased electoral volatility in Belgium. In the mean time, the very stable Belgian electoral system experienced a – quite – important change with the implementation of a five per cent electoral threshold in both federal and regional elections. Therefore, can the introduction of this legal threshold explain – some part of – the increased electoral volatility in Belgium? The last five general elections – three federal (2003, 2007 and 2010) and two regional (2004 and 2009) offer a fertile ground for such an investigation. More specifically, in order to provide an answer to this question, we look at the psychological effect, as coined by Duverger and since then much refined. In addition to the existence of a mechanical effect, the electoral system may have a psychological impact on both voters and parties. Indeed, voters and party elites may adapt their behaviour to the implementation of the electoral threshold and this adaptation could explain electoral volatility. To test this hypothesis, we use several formulas in order to measure the psychological impacts of the five per cent threshold on Belgian voters, on the one hand, and on Belgian political parties, on the other hand. Our results show the impact of the legal threshold should be nuanced. While there was in fact an impact – both mechanical and psychological – on parties, it did not prevent the emergence of new political parties – which may explain some part of the electoral volatility. As of the voters, when they are aware of the threshold, they tend not think of the legal electoral threshold in the polling booths, so the main explanations for electoral volatility should be sought elsewhere.