Spatial Models of Politics

Spatial models are widely used by political scientists to analyze decision making in a wide range of settings, from elections and legislatures, to government formation, to international organizations, to the U.S. Supreme Court, and many other things. Spatial models provide what has proved to be a fruitful way to think rigorously about politics, grounded in a simple intuition with a reach far beyond the narrow confines of professional political science. At least since the days of the French Revolution, indeed, references to “left” and “right” and to changing policy “positions” have been a part of day-to-day political discourse. The general public generally understands what it means to talk about politics using “spatial” language, as such language is not just a conceit of political scientists. In this entry, mathematical and empirical approaches to spatial modeling and their applications to various forms of political decision making are discussed.

The words left and right refer in this context to directions along a “dimension” of political preference. But one dimension is rarely enough for a good description of how real people think in a given setting. It is easy to imagine two people who are both on the economic right, with similar views about government intervention in the economy, who nonetheless have very different views about government intervention in matters of personal morality. One can think of views on matters such as abortion and same-sex marriage, for example, in terms of a liberal–conservative dimension that is quite independent from—in spatial language orthogonal to—the left–right dimension. If economic and social issues are all that concern political scientists, then they can consider political preferences to be well described using a two-dimensional space, spanned by a left–right economic policy dimension and a liberal–conservative social policy dimension. Building systematically on this spatial metaphor for describing political preferences, a metaphor that does seem to be deeply rooted in real politics, political scientists tend to take one of two distinct but related approaches when they analyze political decision making. These approaches can be thought of as mathematical and empirical.