I like to be devil’s advocate among my friends, and since MAPLight and Sunlight are some of my friends, they can’t get out of a careful look over their analyses. Ellen writes on her blog about an analysis provided by MAPLight of the correlation of contributions to representatives and their vote on H.R. 1424 (bill | vote | MAPLight page):

They found that those “interested” in the legislation, both pro and con, gave over $8,000 more to the individual legislators who voted the way they wanted them to. A press release from Maplight.org gives more detail:

Opponents–such as Accident and Health Insurance, Big Business, Chambers of Commerce, Restaurant and Manufacturing, Retail and Wholesale Trade gave an average of $22,693 to legislators who voted No on this bill, compared to $14,183 to legislators who voted Yes. The disparity is 160% [JT- that’s 60%!] more money given to a No vote.

Supporters–such as Health and Welfare, Mental Health care-givers, Mental Health Services, Clergy and Non-profit–gave an average of $4,242 to legislators who voted Yes on this bill, compared to $1,812 to legislators who voted No. The disparity is 234% more money [JT- should be 134%] given to a Yes vote, or $2,430.

…. Dan Newman, MAPLight.org’s director, … points out that campaign contributions are just one factor in determining how a legislator votes, and they do not claim one caused the other. “We do make the claim, however, that campaign contributions bias our legislative system,” he adds. “Simply put, candidates who take positions contrary to industry interests are unlikely to receive industry funds and thus have fewer resources for their election campaigns than those who vote in favor.”

I don’t suggest the numbers reported are wrong (well, actually, the percent changes are wrong), but the relevant disparity in money, as far is it could be tempting motivation for a legislator to change his position, is much smaller than MAPLight reports.

The trouble with MAPLight’s analysis of the correlation, even putting causality aside, is that contributions are correlated with party membership, and so are votes. So it’s no surprise there is a correlation between money and votes. If I give only to Democrats and equally to all Democrats, it will appear as if I’m giving money only to those voting in favor of Democratic issues — even though my contributions have not taken into account any particular issue position. Further, and importantly, even though you will see this correlation between my money and votes, it does not mean there is any incentive for a Democrat to change his position on an issue. That’s because in my hypothetical I am giving equally to all Democrats. The only incentive is for a Republican to become a Democrat to get some of my money, but that rarely happens. Bottom line: correlation doesn’t immediately establish incentive.

Returning to H.R. 1424, what we need to do is split the Members by party. The incentive for a Democrat can only be established by looking at the money going to Democrats. In this case, only three Democrats voted No on the bill, and three Democrats is not a large enough sample to come to any conclusions about anything (t-test be damned).

As for the Republicans, industry groups opposing the bill gave an average of $22,850 to Republicans voting against and $19,525 to those voting in favor (leaving out a clear outlier, in MAPLight’s favor). Yes, more money went to those voting against, but only $3,325. That’s a 17% difference, not a 60% difference. (It’s also a relatively small amount compared to the variability in the contributions just within the yes or no vote groups separately.)

That just leaves the contributions to Republicans from industry groups supporting the bill. Here MAPLight’s point stands. An average of $3,630 went to those voting yes and only $1,865 to those voting No. That’s a big difference, around $1,765, but still smaller than what MAPLight reported.

So here’s the bottom line: The incentives for Members of Congress to vote according to their war chest is far smaller than what is evident from MAPLight’s analysis because representatives are not competing for money going to the other party. By looking at Republicans alone, we see that it is true that money from groups supporting the bill went more to those voting in favor of the bill, but with a difference of only $1,765 (nevertheless, nearly a 100% increase over the no-vote amount). However, while there was a lot more money at play from groups against the bill, the difference between the yes voters and no voters was $3,325 (a 17% increase over the smaller of the figures), a much smaller incentive than the $8,500 reported by MAPLight.