Beautiful Visualization of the Time Evolution of Ideology in the United States Congress

This visualization of the time evolution of ideology in the United States Congress, which constitutes today's xckd, is absolutely gorgeous.

(It reminds me of a visualization that Jim Moody and my collaborator Peter Mucha are publishing in the journal "Network Science". I don't think they have posted that one on a website yet. It also reminds me of Martin Rosvall's "alluvial diagrams".)

The calculations of political ideology were done using DW-Nominate, by the way. I am biased, but I happen to know of a better method to do this. :)