Party-System Extremism
Polarization: ideological elite
Data: eb cses
Use Cases: @ezrow_parties_2008 @dow_partysystem_2011
Description
Party-system extremism, proposed by Ezrow (2008), measures the dispersion of parties’ ideological positions relative to the dispersion of voters’ positions, borrowing from Alvarez and Nagler (2004). Ezrow applies the measure to data from the Eurobarometer, while Dow (2011) uses CSES data.
Operationalization
The weighted version computes as follows:
$$WPE_k=\frac{\sum_{j=1}VS_j|(P_{jk}-\bar{V}_k)|}{\sigma _{V_k}}$$
where: $V_k$ is the average left-right self-placement of respondents in country-year $k$, $P_{jk}$ is the ideological position of party $j$ in country-year $k$, $VS_j$ is the vote share for party $j$, and $\sigma_{vk}$ is the standard deviation of respondents’ left-right self-placement in country-year $k$. The unweighted version is computed as follows:
$$UPE_k= \frac{[\sum_{j=1}|(P_{jk}-\bar{V}_k)|]/n}{\sigma _{V_k}}$$
where $n$ is the absolute number of parties in country-year $k$.
Use cases
Publication that use this measure:
| Title | Authors |
|---|---|
| Party-System Extremism in Majoritarian and Proportional Electoral Systems | Dow (2011) |
| Parties’ Policy Programmes and the Dog that Didn’t Bark | Ezrow (2008) |