Similarity

One popular vein of analysis in sports commentary is doing "similarity scores" for different athletes. By analyzing the past career of a current player and seeing which older players he's similar to, you can glean information about his likely future trajectory. Nate Silver, who mainly does quantitative sports analysis though he's recently become known for his political blogging, has done something similar for American states based on a variety of political and demographic factors.

It's an interesting exercise and shows, among other things, that there's less similarity than I might have thought out there. A number of states, including very large ones like Florida and Texas, are essentially unique by this standard and the closest any pair gets (North Carolina and South Carolina) is 71 out of 100.