Efficient Markets in Legislation?
In any popularly elected legislature, there are only two margins of victory that make sense: winning by one vote, and winning all of them. Since the senate has 100 members, it's easiest to convert to and from percentages, so let's consider them: imagine a bill that looks like it's going to pass with 60 votes. It obviously only needs 51. So if there's any way to modify the bill such that it's less appealing to nine senators but more appealing to 51 (or unappealing enough to some senators, such that it loses nine votes, but more appealing to the remaining 51 voters), everyone involved has every incentive to back those changes: the 51 voters-in-favor get to vote for a bill they like more, while the nine new voters-against can now vote against something they don't like. Assuming an evenly-divided legislature, you can classify those bills as "I am a Republican" or "I am a Democrat" bills -- they do everything possible to benefit the narrow majority that supports them, while staying unappealing to the opposition half of neutral voters.
But there are other bills, like the PATRIOT act and various censures and resolutions, which tend to pass with 99 or 100 votes. Those obviously aren't "I'm a Democrat/Republican" bills, but someone's support of them doesn't have any informational content, so I'd consider them "I am an American." bills. Or perhaps "I am not in favor of illegalizing ice cream and puppies." bills. The interesting thing about these bills is that they show exactly the opposite tendency as partisan-identity legislation: if a new resolution has the support of 90 members, every one of those 90 has every reason to lard it with a little more meaningless rhetoric, which puts the remaining 10 in an increasingly dicey situation.
If you imagine bills being proposed at random, it's obvious that they gravitate towards the nearest pole: if they have more than 75 votes in favor, they should reach 100; if they have between 25 and 75, they should find their way to 51 or 49 -- and otherwise, they should end up at 0.[1] In my experience, though, these voting margins are common, but not universal. Here are a few possible explanations:
- Inefficient negotiations markets: it's just not worth everybody's time to squeeze in a little more pork, so politicians will leave a bill alone as it gets closer to 50/50 support.
- Too atomic: maybe this happens one session at a time, or one career at a time. "Logrolling" could account for some of this, too: one bill might get a few extra votes in exchange for another bill getting just the right number to pass (obviously, in an efficient market this would have no net effect, since a vote-due-to-logrolling is as much a part of a 51-vote bloc as any other. But it's harder to account for when adjusting the terms of a bill, so it feeds into the first explanation).
- Politicians are underrated: as painful as it is for a libertarian to say this, maybe politicians are actually voting on principle, and this cynical vote-trading stuff just doesn't appeal to them.
If explanations #1 and #2 are correct, we'd get less pork if we had smaller legislatures, because the marginal utility of changing a bill would be less constant.[2] If explanation #3 is correct, we are lucky, indeed -- as long as they're smart.
[1] Obviously, that doesn't happen. But bills that start out with few prospects of passing, and continue to lose support, just get dropped -- so it's survivorship bias.
[2] Unless one of the constraints is lack of information about other legislators' preferences.