The US isn’t principally crimson or principally blue. It’s principally purple. That’s what I’ve realized from a quarter-century of constructing maps based mostly on the outcomes of presidential elections.
The nation is, nevertheless, changing into extra break up alongside occasion traces.
This work began as a curiosity undertaking. Again in 2000, most maps of election outcomes confirmed states coloured both crimson or blue relying on which aspect had extra votes in that state – Republican George W. Bush or Democrat Al Gore. However that one-or-the-other strategy didn’t match up with an election that was so shut, it was in the end determined by 537 votes in Florida.
In 2000, an election map confirmed counties coloured based mostly on who they voted for within the presidential election.
USA At present by way of ESRI
I reside in Belle Mead, New Jersey, which is 8 miles north of Princeton, the place I educate. I’m in Somerset County; Princeton is in Mercer County. Mercer County was blue in that election, however neighboring Somerset was crimson.
That impressed me to take a look at the precise knowledge used for the map. In Somerset County, about 51% of the votes had been for Bush and about 48% for Gore.
To me, that was disappointing: Why paint Somerset County crimson when it was nearly a tie?
I wished to write down a pc program to make my very own county-by-county map exhibiting not simply the winner, however the mixture of voter preferences. On the time, I used to be educating a course known as “Computer Methods for Problem Solving.” I believed it may very well be an attention-grabbing remaining undertaking for that class to have the scholars make a map that used shadings of crimson or blue based mostly on vote totals for every occasion’s candidate.
My colleague Alain Kornhauser helped me get geographic knowledge about every county within the nation, so I might match them up with vote totals, which I’ve principally gotten from knowledge compiled by Dave Leip. I wrote my very own code to create such a map, however I didn’t really use that concept as the ultimate undertaking for the category that 12 months. I used to be pondering I might use it as the ultimate undertaking the following 12 months.
However I did put my “Purple America” map on my college webpage. And there it sat for 4 years, largely unnoticed.
The unique ‘Purple America’ map from 2000.
Robert J. Vanderbei
A glance via time
About 4 years later, somebody found my Purple America webpage. Once I regarded on the site visitors knowledge, I discovered it had gone viral.
Ever since, after every presidential election, I’ve been making that 12 months’s model of the map. I went again and did all of the elections since 1960 as effectively. As I’ve written by myself web site, these maps are nonetheless doubtlessly deceptive as a result of a densely populated space like New York Metropolis takes up a small space, whereas a sparsely populated space like Montana takes up quite a lot of area. However they nonetheless present a clearer image of a rustic that’s not simply crimson or blue.
America stays a purple nation after the 2024 election, however much less so than in previous years.
Robert Vanderbei
Over time, these maps have proven the U.S. changing into extra geographically polarized. In 2024, most counties lean strongly towards both crimson or blue. Some are nonetheless purple, however there are fewer of them, and so they’re much less purple than they was once.