More Election Cartography Primers

The New York Times

Today, print subscribers to the New York Times were treated to a fold-out map showing a choropleth map of the 2012 election results at the ZIP code level (above). “The map is part of a special election section that aims to help explain the political geography of the United States — identifying where people who are conservative and liberal live and pointing out how physical boundaries, like the Rio Grande and the Cascade Mountains, often align with political ones,” writes the Times’s Alicia Parlapiano.

Parlapiano’s piece is in fact a lengthy tutorial on how to read election maps, along the lines of the pages I linked to in last week’s post on election map cartography—it outlines the problems of state-level election maps and choropleth maps that privilege area over population, for example, and shows some other ways of depicting the results.

It can’t be a coincidence that in today’s Washington Post we have Lazaro Gamio’s article dramatically highlighting the difference between area and population size with comparative maps. Mark Newman’s cartograms also make an appearance.

I can only conclude that both the Times and the Post are making efforts to educate their readers before the election results start coming in, one week from tonight. (Deep breath.)

A Primer on Election Map Cartography

With less than two weeks before the 2016 U.S. presidential election, it’s time for a refresher on election map cartography, particularly in the context of U.S. presidential elections.


2012 U.S. presidential results. At right, a cartogram scaled by electoral vote. Maps by Mark Newman.
2012 U.S. presidential results. At right, a cartogram scaled by electoral vote. Maps by Mark Newman.

Let’s start with the basics: at All Over the Map, Greg Miller explains the problem with U.S. presidential election maps—big states with few electoral votes look more important than smaller states with more votes—and introduces the idea of the cartogram: a map distorted to account for some variable other than land area.

Here are some cartograms of the 2012 U.S. presidential results (see above). Previously: Cartograms for the 2008 U.S. Presidential Election Results.

The Map That Started It All

Scribner's statistical atlas of the United States,
Plate 11: Popular Vote: 1880. From Fletcher W. Hewes and Henry Gannett, Scribner’s Statistical Atlas of the United States, 1883. Library of Congress.

Back in 2014, Susan Schulten looked at the map that may have started it all: an 1883 choropleth map of the 1880 U.S. presidential results (see above) that shows results not only on a county-by-county basis, but also the amount the winning candidate won by.

The map may not look advanced today, but in 1883 it broke new ground by enabling Americans to visualize the spatial dynamics of political power. Readers responded enthusiastically. One reviewer pointed to the Republican counties in Arkansas—something left invisible on a map of the Electoral College returns—and wondered what other oddities of geography and history might be uncovered when election returns were more systematically measured. In other words, the map revealed spatial patterns and relationships that might otherwise remain hidden, or only known anecdotally. Perhaps its no coincidence that at the same time the two parties began to launch more coordinated, disciplined, nationwide campaigns, creating a system of two-party rule that we have lived with ever since.

(This map also inverts the modern colours for the two main U.S. political parties: here the Democrats are red and the Republicans are blue. Those colours were standardized only fairly recently.) [Geolounge]

Rethinking Election Map Design

Back to Greg Miller, who has a roundup of different kinds of election maps throughout history, including the maps we’ve seen here so far, Andy Woodruff’s value-by-alpha maps (previously) and others.

For other ways of mapping election results, see this gallery of thematic maps, which includes things like 3D choropleth maps, dot density maps, and all kinds of variations on cartograms and choropleth maps. There’s more than one way to map an election. [Andy Woodruff]

Mapping Clinton and Trump’s Upside Potential (Whatever That Means)


Earlier this month FiveThirtyEight built a county-by-county model showing where both Hillary Clinton and Donald Trump’s “upside potential” — by which they meant where they would each benefit from the shifts in the electoral landscape. Compared to 2012, Clinton is underperforming with non-college-educated whites and Trump is underperforming with Asians, African-Americans, Latinos and college educated whites.

To get a handle on how these shifts could affect the electoral landscape, we modeled how many of Romney’s votes came from college-educated whites and minorities and how many of Obama’s votes came from non-college-educated whites in each state, county and congressional district. The difference between these two vote totals, shown in the map above, can tell us where Clinton and Trump have the most potential to build on 2012.

The authors went on to game out what that might look like in terms of the electoral vote if one in five voters in those shifting groups switched allegiances.

Trump, Clinton and the Gender Gap

A pronounced gender split is emerging in the 2016 U.S. presidential election. Based on national polls in October, Nate Silver writes, “on average, Clinton leads Trump by 15 percentage points among women while trailing him by 5 points among men. How would that look on the electoral map?” Silver does a quick-and-dirty estimation by adding or subtracting 10 points to/from the FiveThirtyEight forecast. Moving 10 points to Clinton’s column approximates what the electoral map would look like if only women voted:


Moving those 10 points to Trump’s column approximates the results if only men voted:


You’ve almost certainly seen these maps make the rounds of social media. This is where they came from and how they were made.

Mapping Berlin’s Election Results


The Berliner Morgenpost has an interactive map showing the results of the Berlin state elections held on 18 September 2016. (Berlin is a state in its own right.) The choropleth map is shaded to show the margin of plurality; more information is given when you hover over or click on a particular district. The biggest gains were made by the right-wing Alternative für Deutschland and liberal Freie Demokratische Partei; the Pirate Party, which won 15 seats in 2011, was wiped out. [Maps Mania]

Mapping the Spanish General Elections

El Mundo, 27 June 2016

Spain held elections for its legislature, the Cortes Generales, on Sunday. Spain’s Congress of Deputies is elected via proportional representation, so the constituency map model we’re used to in anglophone countries doesn’t apply. How then are the results mapped? If the interactive maps from El Mundo (see screencap above) and El Diario are any indication, by municipality. El Mundo’s map also allows you to filter by political party and toggle between municipal and provincial results (Senate seats are by province); El Diario’s has some simple demographic filters. [Maps Mania/Maps on the Web]

Mapping the EU Referendum Results

Maps of the results of the United Kingdom’s referendum on remaining in the European Union show several different ways of presenting the results.

The BBC’s election night map is bare-bones, showing which side won which local authority, but not by how much. Appropriate for the moment, and for finding your locality, but not necessarily very revealing.

The New York Times

The New York Times’s map, another example of the fine work done by their graphics department, is a choropleth map that indicates the margin of victory in each local authority. It shows the intensity of the win by each side. (The Times does something similar with a hexagon grid map.)

The Guardian

But the EU referendum isn’t like a general election, where each electoral district has roughly the same population, and counts the the same in parliament. In this case it’s the raw vote numbers that count, and local districts can vary in size by as much as a couple of orders of magnitude. So the Guardian’s approach (at right), a hexagon grid that combines a choropleth map with a cartogram to show both the margin of victory and the size of the electorate, is probably most fit for purpose in this case.

I’m actively looking for other maps of the EU referendum results. Send me links, and I’ll update this post below.

Continue reading “Mapping the EU Referendum Results”

Hillary Clinton in the Primaries: 2008 vs. 2016


Geoffrey Skelley compares the percentage of the Democratic primary vote won by Hillary Clinton in 2008 with the percentage she won in 2016: among other things, she was up sharply in the Deep South and down sharply in the industrial Midwest and Appalachia. “While the universe of voters participating in 2008 and then 2016 changed considerably thanks to mobility, interest, and mortality, our map suggests that many ’08 Clinton voters became ’16 Sanders voters, and many ’08 Obama voters became ’16 Clinton voters.” [Daily Kos]

‘There Is More to Gerrymandering Than Ugly Shapes’

On the liberal political blog Daily Kos, Stephen Wolf argues that it takes more than a weirdly shaped electoral district to make a gerrymander:

Land does not vote and we can’t judge gerrymanders simply based on geometry. Districts aren’t just abstract shapes on a map, but collections of actual people and voters. Ultimately, the outcomes produced by a particular map matter far more than a map’s appearance. Comparing the actual congressional districts to plausible alternatives in Maryland and other states demonstrates both how gerrymandering is more complex than merely grotesque shapes, and that Maryland is far from the worst partisan gerrymander nationwide.

How to Circulate a Fake Election Map

fake-uk-elections BuzzFeed’s Jim Waterson calls out a map making the social media rounds that purports to show the results of the 2016 local elections in the U.K. Only it doesn’t. It’s apparently being spread by Labour supporters keen to defend their party’s performance in the elections and convinced their party is receiving unfair media treatment—and of course, people tend to believe what they want to believe. Waterson goes on to show how to make a fake map of your very own. [Thierry Gregorius]

Previously: When Maps Lie.