Changes in the location of the median voter in the US House of Representatives, 1963-1996

We consider the degree of ideological polarization within and between the p arties in the U.S. House of Representatives for the period 1963-1996, using the Groseclose, Levitt and Snyder (1996) adjustment method for ADA and ACU scores to ensure over time comparability of roll call voting data. We focu s especially on the median House member, since we believe that change in th e median offers a better measure of the impact of the change in party contr ol than does changes in the mean roll-call voting score. Our data analysis makes two general points. First and foremost, when we loo ked at the change in the location of the House median voter, we found a dra matic change after the Republicans gained a majority in the House in 1994. After the Republicans became a majority in the House, the ADA median in the House in 1995-1996 was at 24, far closer to the Republican median of 4 tha n to the Democratic median of 83. The shift in median from 1993-1994 to 199 4-1995 involved a change of over 25 points in one election - far and away t he greatest single shift in ideology of the modern era. In contrast, the me an changed only 1 point over this same period. Second, for the three decade s we investigated, we found three historical epochs vis a vis the relative locations of the ADA (or ACU) floor median and the ADA (or ACU) floor mean in the U.S. House of Representatives - two inflection points in 1983 and 19 94 which are related to trends in regional realignment.