History of US Legislative and Executive power

Following the recent (midterm) US elections and looking at this article over at the Economist, I was fascinated by the graphic they provided at the bottom detailing periods of Democrat and Republican control over the House of Representatives and the Senate. The obvious missing information was on presidential control, so I did one up myself. You can grab it (as an Excel spreadsheet) here.

It’s interesting to note that since 1901, the Democrats have generally been dominant in the House of Representatives (64.8% of overall control) and the Senate (57.4%), but the Republicans have maintained a slight upper hand in the Presidency (48.1% Democrat).

Americans do seem to prefer having just one party in control at a time (59.3% of the time all three are under the control of the same party rather than the 25% that would have been expected by pure chance).

Update: I have redone this following the 2008 election here.