The V-Dem Party Institutionalization Index: a new global indicator (1900-2015)

Because levels of party institutionalization may affect the availability of good data, existing datasets have limited reliability and coverage. To overcome these problems, we introduce the V-Dem Party Institutionalization Index, the first global country-level index on the issue. It covers – as of May 2017 – 173 countries for 116 years (1900-2016). Its geographical coverage, timespan, and conceptual reach are larger than any existing alternative. We offer an additive index that measures the scope and depth of party institutionalization in a country every year. Scope is measured by the proportion of parties that reach a threshold of minimal institutionalization, while the linkages party establish with the masses and the elites define the depth. Exploring a set of well-known cases, we show that: the index has extensive face validity, is consistent across regime types, and is comparable to other established indicators of institutionalization.