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The case for Choropleth maps on Wikipedia election articles

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Note: "Choropleth" means "cluster zones". A Choropleth map is a map that uses different hues of the same color, for the clustered variable.


Typically, election maps on Wikimedia Commons and Wikipedia display the jurisdiction's constituencies ("districts", "ridings", "wards", etc.) colored by the party that won it. This makes perfect sense: under Plurality (First-past-the-post), whoever tops the district, gets the seat.

However, under the various forms of Proportional Representation, no-one "wins" a district: districts are multi-member, and coming first is no more meaningful than coming second, only the share of votes is (which by design gives the share of seats).

As a reminder, PR methods are in use in:

  • almost all of continental Europe and Latin America, in elections of legislative assemblies (exceptions: the French Parliament, the Polish and Czech Senates, and a number of countries using FPTP in parallel with PR seats).
  • in English-speaking countries, this includes: the lower houses of Ireland, Northern Ireland (STV), New Zealand, Scotland, Wales (MMP), and the upper houses of Australia.

(That is, in summary, most liberal democracies and jurisdictions!)

As the examples below show, using maps of district winners for PR elections has many shortcomings:

  • lack of information provided:
    • in a two-party system, a big *victory for one party is a big loss for the other ; but in a multi-party PR system, it is impossible to tell with a district winner map, areas in which the party came second, from areas where it is completely excluded
    • in PR, district victory is arbitrary: the party coming first may have received as little as 20%, and may be followed by a series of like-minded parties that collectively outweigh the first party in the district
  • meaninglessness:
    • due to Duverger's Law, PR methods tend to increase the number of parties in competition, division being much less detrimental ; but this doesn't mean there can't be pre-declared left-right alliances, which in this case is the meaningful division to show
    • under FPTP, parties tend to be catch-all parties ; under PR, coalitions may be formed after the election and can aggregate catch-all parties with smaller parties appealing to a fraction of the electorate, and sometimes one-issue parties
  • lack of legibility:
    • the number of colors needed in a multi-party system makes maps uneasy to read and of little use

Illustrating the absurdity

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Most electoral maps on Wikipedia show district winners even under Proportional Representation, despite it is in such case meaningless, potentially deceptive for election analyses, and illegible overall:

Some designers prefer to color small dots or squares representing seats, instead of representing zones. Their legibility is questionable:

Solution

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If one wants to analyze an election under PR, then one should better use party-specific choropleth maps, which use hue progression to show the varying degrees of success in the various districts. The degrees should be divided in 4 or 5 natural breaks (Jenks): this method allows readers to extract the most meaning (unlike arbitrary intervals, or standard deviation) while staying very close to the distribution of data.

I have often seen these maps in use by political pundits, "psephologist"s, and sociologists in continental Europe, in particular France and Germany. The English Wikipedia is largely written by users who do not live in countries using PR, and this probably explains why it hasn't caught up on that particular custom of political science in non-English-speaking countries.

As a sidenote, it could be argued that chorochromatic maps would be more accurate than choropleth ones, especially when a state has districts with largely unpopulated areas, such as the Australian Outback (for upper house elections), the Scandinavian polar circle, the Kazakh Steppe, Russian Siberia etc.

Illustrations

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Here's a list of choropleth election maps posted on Wikimedia:

Bulgaria

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Excellent map made this year by User:Ivonster04. Uses 5 hues with a rough clustering adapted to each party, that works very well. With maps like this you can understand Bulgarian politics very quickly!

Beautiful summary of the April 2021 Bulgarian parliamentary election

Czechia

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Czech Wikipedia User MrGreg has created about a hundred maps, solely for Czech elections (legislative since 1992, presidential runoffs since 2013).

  • For legislative elections, he always uses the same scale of 8 hues, each corresponding to 5% intervals (range [0-5;35-40]). In some cases he has to manually label districts that are above 40%.
  • For presidential run-off elections, he also uses 8 hues but with a larger interval of 10% (range [<20;>80]).

He also has two maps of district turnout variations, using 9 hues corresponding to 2.5% intervals [<-10;>10], and two maps of district turnout, using the range of presidential run-off elections.

All in all, they are very legible, and provide immediate insight of each party's strong areas.

Complete gallery of MrGreg's maps

Presidential elections

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Legislative elections

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Finland

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Made by commons:User:Stadscykel in 2011. Used 5% intervals (except for the first 10 percent, and the last interval), which means there were from 7 to 10 hues for the 4 bigger parties. Did not contribute later. PS 2015 was made by commons:User:URunICon.

See also: commons:Maps of Finland - general elections by year and party.

Germany

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de:User:Wahlatlas, apparently the owner of the website of the same name, made these wonderful maps, with 5 degrees and (seemingly) natural breaks.

User:Furfur made these maps for the 2009 election. The number of intervals range from 4 to 9 (!) because of the 5%-interval chosen arbitrarily.

User:Hilarus von Baerenstein uploaded just one beautiful map, with 6 intervals adapted to each party chosen manually:

Here, the use of hues for different intervals provides many clues to our understanding of Germany before WWII:

Ireland (Republic of)

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Excellent maps were made by User:JandK87 for Ireland's Dail elections (since 1921) and Northern Assembly (since 1973). However, he stopped editing after 2011, came back for the 2016 election, and never edited again. It turns out that another user made and imposed his own maps starting in 2011, where seats won are shown as tiny dots on a dark grey map. see Category:Election maps of the Republic of Ireland on Commons

Ireland (Northern)

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Made by User:RaviC:

Japan

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commons:User:沁水湾 made many electoral maps, including one that defines as a choropleth map using 5 hues:

In 2022, she crafted 7 maps for the 2021 Japanese general election, one for each party that won seats through the PR method:

...she even added them on the election page with a switcher!

Kazakhstan

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commons:User:ShadZ01 recently produced these awesome maps of the most recent Kazakh elections (2019 and 2021). There are 4 intervals for the minor parties and 5 for the dominant party, which makes sense. The ranges do not seem to be broken with a statistical tool, but rather manually. No legend whatsoever is included; it has to be written somewhere else.

Although this map is quite old, it remains that Kazakhstan's peculiar population density would make the case for the use of Chorochromatic maps (using the data patterns) rather than choropleth (using political boundaries)

2021 Kazakh legislative election:

Performance by Nur Otan by region.
     0–55%          55–60%        60–65%
     70–75%        75–80%
Performance by the Ak Zhol Democratic Party by region.
     8–10%          10–12%        12–14%
     14–16%
Performance by the People's Party by region.
     0–5%          5–10%        10–15%
     15–17%
Performance by the Auyl People's Democratic Patriotic Party by region.
     0–4%          4–8%        8–12%
     12–13%
Performance by Adal by region.
     0–2%          2–4%        4–6%
     6–7%

Korea (Republic of)

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made by commons:User:沁水湾

Netherlands

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Nepal

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Made by commons:User:Vanished user 1932142 in 2020. Used 6 hues, corresponding to 3-percent-intervals:

Congress at the 2017 provincial elections

Poland

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Made by Robert Wielgórski, known by the username Barry Kent (commons) (also wp:pl wp:en) right after the 2007 elections. He made use of varying interval numbers and lengths for each party.

Portugal

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User:Welkend (commons) has just made awesome maps for the 2022 Portuguese legislative election, using 5 intervals for each party. Intervals are all of equal size (except PS's first one?) which highlights voter concentration:

Scandinavia: Sweden, Norway, Denmark

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Sweden

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Several interesting maps were done by User:Avopeas who was mostly active in 2017, and blanked his talk page in 2019. He is still active on commons (User page) where he updates average polling graphs for Scandinavian countries.

Christian Democrats results in the 2014 Swedish general election. The Christian Democrats obtained considerable support in the Christian area in southern Sweden.
  • (+) we can clearly see the best and worst areas for each party
  • (-) All the maps use the same orange tone.
  • (-) More problematic, the maps use 14 equal intervals and different hues! Impossible to process quickly.
  • (-) the equal intervals are not adapted to each party (ranges are too large for smaller parties, too small for larger ones)

The author did much better with this map of population density, although the intervals are quite arbitrary.

2014 Swedish general election § Results by municipality

Results of the 2018 Swedish general election

2002 Swedish general election and 2006 Swedish general election (the two blocs received >97%):

Feminist Initiative and Sweden Democrats:

Norway

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2017 Norwegian parliamentary election.

2021 Norwegian parliamentary election.

Denmark

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Denmark 2015 (blocs)

Slovakia and others

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Australian User:Erinthecute, who has made countless illustration maps for election pages on Wikipedia, recently began to notice the usefulness of choropleth maps, beginning with Slovakia, the city of Graz (see § Cities) and Portugal. She is using 4 to 6 hues by party, usually 5:

commons:User:Liqid1010 made a handful of maps following the 2020 Slovak parliamentary election, using nine 5%-intervals.

sk:User:Mikulas1 crafted many maps in 2017, but sadly, stopped contributing. His maps, using for each party a variable number of (mostly) 5%-intervals, have not yet been integrated into Wikipedia's English articles on Slovak parties and elections:

Other choropleth maps of elections in Slovakia found:

South Africa

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commons:User:沁水湾 attempted to mix two types of maps, one large with bullet points for seats, the others are small party-specific choropleth maps with number. I am not sure the first one is necessary at all, and removing it would increase the size of choropleth maps, making the numbers legible.

Turkey

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Turkish User:Nub Cake made these choropleth maps of the performance of Turkish political parties over the recent years. There are 7 hues, but the margins are not provided:

With the help of User:Nub Cake, User:Mondolkiri, who is now banned from editing, made these maps using 10% intervals:

Previously, User:Emreculha made other maps for Turkish parties' performance, using a wide palette of hues, representing 5% intervals (which leads to similar legibility issues as for Swedish/Norwegian maps).

User:QuartierLatin1968 made these maps in 2007 using a color gradient instead of discrete hues. The result is more legible than 10 or 20 hues. The user is still contributing to Wikipedia projects.

User:MustafaKurt and User:Bibilili

Ukraine

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Made by commons:User:Tohaomg (also uk:Користувач:Tohaomg) following the 2019 snap elections. The number of intervals varies between 5 and 9. The ranges are ad hoc. Excellent to understand where parties are strong and weak. The hues are not, however, standardized (leaving the impression that the 3rd party came in front of the 1st).

The first modern Ukrainian election per se:

Maps for the period between 1994 and 2002 (besides turnout) were made by commons:User:Nazar.galitskyj in 2013-14 and 2019. Uses few hues, but very informative:

commons:User:DemocracyATwork contributed solely to Wikipedia between 2008 and 2010 to upload content about Ukrainian elections:

Well-done maps at the district level were made back in 2006 by User:Olegzima:

commons:User:DemocracyATwork made the same maps twice -- one highlighting regional strongholds (using the shares of the parties' nationwide votes), the other showing regional success (relative to other parties in the region):

2007 Rada elections
Maps showing the top six parties support - percentage of total national vote (minimal text)
Party of Regions results (34.37%)
Party of Regions results (34.37%)
Bloc Yulia Tymoshenko results (30.71%
Bloc Yulia Tymoshenko results (30.71%
Our Ukraine People's Self-Defence results (14.15%)
Our Ukraine People's Self-Defence results (14.15%)
Communist Party of Ukraine results (5.39%)
Communist Party of Ukraine results (5.39%)
Bloc Lytvyn Party results (3.96%)
Bloc Lytvyn Party results (3.96%)
Socialist Party of Ukraine results (2.86%)
Socialist Party of Ukraine results (2.86%)
2007 Rada elections
Maps showing the top six parties support - percentage per region
Party of Regions results (34.37%)
Party of Regions results (34.37%)
Bloc Yulia Tymoshenko results (30.71%
Bloc Yulia Tymoshenko results (30.71%
Our Ukraine People's Self-Defence results (14.15%)
Our Ukraine People's Self-Defence results (14.15%)
Communist Party of Ukraine results (5.39%)
Communist Party of Ukraine results (5.39%)
Bloc Lytvyn Party results (3.96%)
Bloc Lytvyn Party results (3.96%)
Socialist Party of Ukraine results (2.86%)
Socialist Party of Ukraine results (2.86%)


User:Green Zero (commons:User:Green Zero) made these maps for the 2014 Ukrainian presidential election:

Порошенко Petro Poroshenko (54.70%) Тимошенко Yulia Tymoshenko (12.81%) Ляшко Oleh Liashko (8.32%)
Гриценко Anatoliy Hrytsenko (5.48%) Тігіпко Serhiy Tihipko (5.23%) Добкін Mykhailo Dobkin (3.03%)
Рабінович Vadim Rabinovich (2.25%) Богомолець Olga Bogomolets (1.91%) Симоненко Petro Symonenko (1.51%)
Тягнибок Oleh Tyahnybok (1.16%) Ярош (0.70%) Гриненко (0.40%)
Коновалюк (0.38%) Бойко (0.19%) Маломуж (0.13%)
Кузьмін (0.10%) Куйбіда (0.06%) Клименко (0.05%)
Цушко (0.05%) Саранов (0.03%) Шкіряк (0.02%)

United Kingdom

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Scotland

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commons:User:Brythones and commons:User:MrPenguin20 made these maps in 2016-2017, using 5% or 2.5% intervals:

commons:User:沁水湾 just made these pretty maps, using 5% intervals, which in this case works very fine:

United States

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Although you would think that the USA, not using Proportional Representation in any circumstance, do not need choropleth maps, commons:User:沁水湾 has found a very good use, with multi-candidate primaries. She uses 5% intervals, which makes extremes very legible:

Similarly, User:MisterElection2001 made choropleth maps for minor presidential candidates, by county:

Cities

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Other interesting uses and types

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Choropleth maps unrelated to elections

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Multi-colored areas

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Mostly used on Wikipedia for the United Kingdom local elections (as each ward has multiple seats)

Cartograms (anamorphosis)

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A very original map combining a cartogram of Czech districts sized by their proportion of catholics, colored in 5 hues depending of their vote for the KDU-ČSL party in 2010.

Various

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commons:User:Magog the Ogre/Political maps

See also

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also see