An Introduction to ANIMATE

When you look at ANIMATE you see a large number of letter tokens that are in motion.

The motion occurs in a time frame that begins with the first Congress in 1789 and ends with the 106th Congress in 2000. Controls in ANIMATE allow you to control how fast this “history” runs and how long history pauses between Congresses.

Each token designates a senator or representative. The token appears on the screen when the legislator enters Congress and disappears whenever the legislator dies, retires, or is defeated for reelection. The letter value of the token represents the legislator’s political party, such as “D” for Democrat or “W” for Whig. Just place the cursor over the token to identify the legislator.

The position of the token on the screen is determined by the legislator’s ideology or, technically, the legislator’s DW-NOMINATE coordinates in two dimensions.

The horizontal dimension has a stable interpretation throughout American history. It is economic left-right. Liberals are on the left and conservatives on the right. Briefly, during the Civil War period, there is a spatial realignment and the dimension represents the conflict over slavery.

The vertical dimension is always far less important than the horizontal dimension, even if legislators are dispersed on that dimension. When the dimension is most important, in the 1830s and 1840s and 1940s, 50s, and 60s, it represents conflict on race, with anti-black being at the top. From the 1870s through the 1930s the second dimension represents conflict on rural-urban lines, with agrarian, rural legislators appearing at the top.

We have provided labels as guides to the axes or, synonymously, dimensions. But it should be recalled that the axes are abstractions that represent the output of a scaling algorithm that is blind to the political party membership of the legislator and to the content of the roll calls being voted on.

Ideology is measured by the DW-NOMINATE scaling procedure of Keith T. Poole and Howard Rosenthal. In the contemporary period, we commonly classify legislators as liberals and conservatives in part because their roll call voting behavior in Congress is very predictable. On one roll call, the liberal side might be supported by Barbara Boxer and all the senators to her left; on another Diane Feinstein and all the senators to her left, including Boxer; on still another by Arlen Specter and all the senators to his left, including Feinstein and Boxer; on still another by Orrin Hatch and all the senators to his left, including Feinstein, Boxer, and Specter. DW-NOMINATE simply provides a quantitative basis for this type of observation and allows us to make similar observations for earlier periods of history.

For a brief introduction to the NOMINATE approach, see:
Ellenberg, Jordan. “Growing Apart: The mathematical evidence for Congress' growing polarization. Slate Posted Wednesday, December 26, 2001, at 7:57 AM PT

To learn more, see:
Poole, Keith T. and Howard Rosenthal, Congress: A Political-Economic History of Roll Call Voting. New York: Oxford University Press, 1997.

The motion you see from a given token represents DW-NOMINATE results. DW-NOMINATE ties together all of American history because it constrains the movement through time of individual legislators to be linear. Actual changes in ideology may be both more complicated and more simple. In recent periods, most of the change occurs when legislators change there party affiliation. So, if you use ANIMATE to track the long career of Strom Thurmond, the motion you see is largely tracking his conversion from Democrat to Republican.

There are two major lessons to take away from ANIMATE. First, over time, you see less and less motion of individual legislators, particularly after the Civil War. This shows the stabilization of the American political system. Second, after the Civil War you will see the major party clusters growing further apart until the turn of the century, then come together and overlap, and beginning in the 1970s draw apart again. That is, throughout most of the twentieth century, political divisions blurred but in the last quarter one sees the polarization of American politics.