Single member districts are always going to give the minority party fewer seats than votes, and the disparity gets larger as the minority party gets smaller.
I wrote last week that the 2013 Utah Legislature will be the second-most Republican group in the past 80 years. Today I saw that the Tribune wrote up a good story framed around my analysis.
The story repeated a common misconception that is worth clearing up. The misconception arises from two statistics that stand at odds with each other:
- In last week’s elections, the median Democratic candidate in Utah’s 75 House races won 28% of the vote.
- Despite winning 28% of the vote, Democrats won only 19% of the seats.
Commenting on the 19% vs 28% difference in the House, here’s what Democratic chair Jim Dabakis told the Tribune: “Those numbers are prima facie [self-evident] evidence of gerrymandering by Republicans.” He continued, “They have far more offices than they deserve from the votes they received because of how they twisted boundaries.”
Let’s be clear about this. The 19% vs 28% difference is not prima facie evidence of gerrymandering. I’ll explain why.
The “cube law” of single member districts
Political scientists have long known that single member districts distort the relationship between votes and seats. In fact, the classic “cube law” predicted the following relationship between votes and seats in an electoral system structured the way ours is1:
The Democrats won 28% of the vote. The cube law pictured above would predict that a party winning 28% of the vote would win only 6% of the legislative seats in the absence of any gerrymandering at all. Democrats won far more than 6% of the seats last week; they won 19%. They outperformed the prediction significantly. Why? It has to do with where Democrats live.
Why residential patterns matter
Imagine if Utah’s Democratic voters were sprinkled evenly around the state rather than concentrated in Salt Lake County and a few other areas. If that were the case, then their 28% of votes would produce 0% of seats; every Republican candidate would win by exactly a 72-28 margin, without any gerrymandering at all.
Given that people usually don’t distribute themselves evenly, but in a more haphazard fashion, the cube law instead predicts a more generous outcome: 6% of the seats for the minority.
As it happens, people in Utah tend to cluster a bit more than that. Because Democrats are clustered in Salt Lake County, they won several seats there. However, an awful lot of the Democratic votes cast elsewhere were wasted in places like Utah County. Even if Democrats were given complete authority to draw legislative district lines in Utah County however they wish, there is no map that they could draw that would ensure a single legislative district in the County with anything close to a Democratic majority. (Here’s the proof.)
The punchline: Single member districts are always going to give the minority party fewer seats than votes, and the disparity gets larger as the minority party gets smaller. I discussed this pattern at length in a previous post (see “Do single member districts hurt Democrats?“).
It’s still possible that a gerrymander happened, but the 19% vs 28% difference is not evidence of it–you have to look elsewhere for evidence. Meanwhile, if you want 28% of the vote to produce 28% of the seats, you have to change our electoral system to proportional representation.
Okay, but did a gerrymander happen?
In the case of Christine Watkins, it might have. The legislature moved a big chunk of (conservative) Duchesne County into her district, which was previously dominated by Carbon County. Maybe that change was made for partisan reasons; maybe it was made for demographic reasons. No matter the reason, it may have contributed to her narrow loss. If it was gerrymandered to hurt her, though, I’m puzzled why Rep. Watkins voted in favor of the change.
Then again, maybe the reason for her loss is that Carbon County has moved dramatically away from the Democratic Party over the past few elections. In fact, between 1992 and 2008 Carbon County made a bigger move to the right than any other county in Utah.