As our friends at "The Fix" report:
In the last three decades, the number of members in the middle in the House dropped from 344 (79 percent of the House) in 1982 to four (.9 percent of the House) in 2013. As the slide suggests, redistricting — the decennial re-drawing of the nation's Congressional lines — plays a major role in that decline. The last two nationwide re-draws have largely been incumbent protection efforts, making Republican districts more Republican and Democratic districts more Democratic. Self-sorting — the growing tendency of people to live around like-minded people — is also a major factor in the disappearance of the ideological middle in the House…
Taken together, there are four — FOUR — members of the ideological middle out of the 535 members of the House and Senate combined. That comes out to approximately .7 percent of the entire Congress. In 1982, by way of comparison, more than 75 percent of Members of Congress were part of the ideological middle. So, in the last 30 years, the middle has lost 74 percent of its membership in Congress.
To underscore this point, check out the graphic below: