Votes for House Representatives, Gerrymandering, and Comet Charts
Zan Armstrong
These are the 12 Districts in North Carolina from 2001-2011. Every 2 years there is an election to determine their representatives in the House of Representatives in Congress.
In the scatterplot to the right, we can see how many people voted in 2006 in each district and what percent of the vote was won by democrats.
The black dot in the center shows the overall results, and the average number of voters per district.
The Democrats won just over 50% of the votes at the state level, but in each district it ranged from 29% to 73%.
In each district, between 106k and 232k people voted.
Here are the results for 2008.
Showing both 2006 and 2008 at once, we can see that there were way more voters in 2008. But, it's hard to tell how this changed from district to district.
We can look at just one district, district 11.
But, it might be easier to see if we used a comet instead of points.
Now, district 11 is shown with a single comet flowing from tail to head, instead of two points.
change in number of votes
Horizontal movement shows change in the number of voters. To the right is an increase, to the left a decrease.
change in % won
change in number of votes
Horizontal movement shows change in the number of voters. To the right is an increase, to the left a decrease.
Vertical movement shows change in the % won by democrats, with going up as an increase and down a decrease.
The blue color reinforces the vertical change, showing that the district became more democratic.
Here is the comet chart for the 2006 to 2008 election in North Carolina
Two districts, shown in shades of red and slanting downwards, went more Republican in 2006 than in 2008.
Two, in grey and flat, stayed nearly the same.
And, the other 8 districts went more for the Democrats, getting bluer and slanting upwards.
But, the most obvious change is how many more people voted in every single district.
Which, perhaps shouldn't be a surprise because it was a presidential election year instead of a midterm.
But, still, the difference is huge. More than twice as many total votes in the Presidential election year of 2008 than the mid-term.
North Carolina: 2006 to 2010
From 2006 to 2010, in aggregate the votes went more Republican
2006 elections
2010 elections
Nearly every district matched the aggregate, with the districts become redder and slanting downwards.
Each comet is a congressional district in North Carolina
2006 elections
2010 elections
But, only two districts changed parties, cancelling each other out.
Each comet is a congressional district in North Carolina
2006 elections
2010 elections
2006: 7 dem, 6 rep
2010: 7 dem, 6 rep
Every district also had more voters in 2010 than 2006, though not as extreme as we saw in 2008
Each comet is a congressional district in North Carolina
2006 elections
2010 elections
2006: 7 dem, 6 rep
2010: 7 dem, 6 rep
North Carolina: 2010 to 2014
There was barely any change at the state level between 2010 and 2014
2010 elections
2014 elections
But, the districts look completely different!
2010 elections
2014 elections
Districts that had been won easily by Democrats in the past, became even more of a landslide
2010 elections
2014 elections
Some very Republican leaning districts also went more Democratic, but not enough to even get close to the 50% line
2010 elections
2014 elections
All 5 competitive districts went more Republican!
2010 elections
2014 elections
Overall, 4 districts "crossed the line" switching from a Democratic win to a Republican win
Each comet is a congressional district in North Carolina
2010 elections
2014 elections
2014: 4 switched from dem to rep
What could have caused these big swings in election results?
Each comet is a congressional district in North Carolina
2010 elections
2014 elections
2014: 4 switched from dem to rep
Every 10 years, the districts in each state are redrawn.
These were redrawn in 2011, between the 2010 and 2014 elections
2001 Congressional Districts
2011 Congressional Districts
Let's look at one important change:
District #10 gains part of Asheville from District #11
% votes won by Dems, by district
2010 elections
2014 elections
District 11
District 10
District #10 gains part of Asheville from District #11
% votes won by Dems, by district
North Carolina voters overall went from 45% to 44% democratic
2010 elections
2014 elections
2010: 7 dem, 6 rep (53% dem)
2014: 3 dem, 10 rep (23% dem)
Massachusetts
2006 to 2008
2008 to 2010
2010 to 2012
2012 to 2014
*redistricting, lost 10th district
California: 2012 to 2014
% votes won by Dems, by district
Each comet is a congressional district in California
2012 elections
2014 elections