clipped from www.zimbio.com

A 21.6% explanation isn’t awful when trying to predict the thoroughly chaotic behavior of people in groups, but we can do better. I’ve looked at ratings of Senators on an progressive political index at Progressive Patriots, and the correlation between Senators’ progressive action score and Senators’ level of bill activity is higher (+0.69). Just by itself, Senators’ progressivism accounts for 48.0% of the variation in bill activity.

The bottom line is that if you’re wanting to understand why some members of the U.S. Senate are more active in bill sponsorship and promotion than other members, ditch party as an explanation. A much better explanation of that variation is the progressivism that a Senator maintains in his or her legislative conduct.