Delegates watch as former president Bill Clinton addresses the Democratic National Convention in Charlotte in September 2012. (Jae C. Hong/AP)

Economic inequality, viewed from a variety of angles, is increasing (for example, see this and this). On political inequality, in Affluence and Influence, Martin Gilens presents evidence that politicians in the United States have increasingly become more responsive to the political preferences of affluent citizens than to poor and middle-class citizens.

What do the experiences of other countries teach us about whether these trends are connected? For example, in Scandinavian countries such as Norway, where incomes are more equally distributed than in the United States, are political parties less likely to over-represent the preferences of the rich?

If economic and political inequality are linked — and politicians are overly responsive to a small affluent group — this implies that each process feeds into the other. Policies that are directed toward promoting the interests of the affluent are likely to further enhance the political influence of this group, and on the flip side, citizens who are not members of the affluent group may become less engaged with politics. Each process can lead both types of inequality to proliferate.

Examining 12 West European democracies, James Adams and I studied political inequality in our article “Who Do European Parties Represent?”. We report (buried in footnote 24) that political parties in European democracies do not display a tendency to disproportionately respond to the political attitudes of affluent groups. Political elites in established democracies, it turns out, may not necessarily respond to the political attitudes of the affluent at the expense of other income groups.

More recently, Jan Rosset, Nathalie Giger, and Julian Bernauer in their article, “More Money, Fewer Problems?” (ungated blog here), study political inequality and economic inequality in 24 democracies. Consistent with our non-finding, these authors also report that political elites do not necessarily over-represent the political preferences of the affluent.

But context matters. In their article, Rosset and colleagues find that in countries with high levels of economic inequality political elites are more likely to disproportionately represent the political attitudes of affluent citizens. Some of the Scandinavian countries in their study, such as  Denmark and especially Norway, display much smaller gaps in the party representation of rich and poor. In other words, levels of economic inequality condition levels of political inequality.

So, do political inequality and economic inequality go together?  The comparative research by Rosset, Giger, and Bernauer suggests that they are related. It is also worth pointing to the opposite conclusion: Societies in which incomes are equally distributed are more likely to be associated with political equality.

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Lawrence Ezrow is a professor of government at the University of Essex in the United Kingdom.