Polarisation in American Politics

Paul Sheehan has a piece in today’s SMH on “Red and Blue America”. His conclusion – that American politics is more ideologically polarised today than in the past – is basically right. But he uses the wrong set of facts to show it. Sheehan argues that we can discern polarisation by looking at how many states are “swing states”. But at best, this tells you about geographic polarisation, not ideological polarisation. And at worst, it tells you that when parties devote a larger share of resources to the same set of states, those states are more likely to be swing states.

The only real way to understand polarisation is to look at the ideological positions of members of Congress. Over the years, political scientists Keith Poole and Howard Rosenthal have done just that, categorising bills on a left-right spectrum to give each member of congress an ideological score, and using the fact that members of Congress overlap to rank consistently across multiple years. From 1980 onward, the Republicans have steadily moved to the right, leaving a significant gulf between the two parties (see graphs here).

Perhaps some enterprising political scientist could do the same for Australia?

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4 Responses to Polarisation in American Politics

  1. Geoff Robinson says:

    James Galbraith from the University of Texas Inequality project argues that Democratic states have higher levels of economic inequality (http://www.salon.com/opinion/feature/2004/09/13/polarized_country/index_np.html).

  2. Andrew Leigh says:

    Geoff, interesting stuff, thanks for the link. I find the same thing for Australia — voters who live in more unequal neighbourhoods are more likely to support the ALP. See http://econrsss.anu.edu.au/~aleigh/pdf/EconomicVoting.pdf

    But alas, this still doesn’t get us any closer to understanding political polarisation in Australia — ie. whether the ALP and Coalition are closer or further apart now than in the past.

  3. Geoff Robinson says:

    I think these revealed preference approaches have a lot to offer political history for the pre-survey epoch (unfortunately that is when it is most interesting). The fact that different parties have different support bases suggests that their policies are different. That Lang Labor and Scullin Labor had different bases suggests they were ideologically divergent. It is a more productive way of analysing political history than trying to elucidate personal motives.

  4. Andrew Leigh says:

    Geoff, couldn’t agree more — I think the kind of research you’re engaged in on this topic is really important. But you need a website, so the rest of us can download your papers!

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