Political polarisation compared: creating the comparative political polarisation index

Abstract

Political polarisation is a pressing political issue, as it can worsen democracy and has been rising in many countries in the past two decades. However, the exact scope of the problem is unclear, because conflicting measurements and conceptualisations have created disagreement about which countries are polarised. Scholars usually only measure one type of polarisation, even though multiple types are salient to the concept. Furthermore, little comparative data are available that measure multiple types of political polarisation simultaneously. This article introduces the comparative political polarisation index (CPPI), which provides a comparative measure of political polarisation that incorporates multiple dimensions of polarisation. This article first conceptualises political polarisation as a four-dimensional concept, operating through ideological and affective aspects and at the mass and elite levels. Then, it creates a comparative index that uses cross-national surveys and party manifesto data to measure all four types in more than 100 countries and over 25 years. This article finds that polarisation has not uniformly risen; only elite affective polarisation rose in this time period. Both types of ideological polarisation stayed stable, and mass affective polarisation decreased. These results encourage a closer look at the relationship between different types of polarisation and specify causes and solutions focused around particular types, rather than viewing political polarisation as uniform.