User:Kahlores/Sandbox/Choropleth maps

The case for Choropleth maps on Wikipedia election articles

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

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:

1972 Dutch general election, 7 parties shown out of 14, missing the meaningful left (PvdA-PPR-D66) and right (KVP-APR-CHU) alliances
2018 Latvian parliamentary election, with 7 different parties
2019 Belgian regional elections, with 8 parties and unnecessary hues
2019 Moldovan parliamentary election, 4 parties
2021 Scottish Parliament election, 4 parties with unnecessary hues for constituencies, but would've been very useful in a map of the regional vote
2022 Finnish county elections, 11 parties of which 8 top at least one district, with 7 hues each. Only problem is that these districts do not matter at all.
2007 Estonian parliamentary election, 5 parties with 4 to 6 hues each

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

2022 Finnish county elections, 1379 squares, with colors for 7 middle parties, 2 minor parties + 1 locally major one
2016 Irish general election, 158 dots
2015 Polish parliamentary election, 460 dots -- can you distinguish Poland A and B?
1998 Northern Ireland Assembly election, 108 dots -- at which size can you distinguish the clear-cut sectarian boundaries?
2018 Slovenian parliamentary election, 88 dots -- can you guess where's Ljubljana and where's the countryside?

Solution

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

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

Bulgaria

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!

Czechia

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.

Miloš Zeman 2018
Jiří Drahoš 2018
SPOLU 2021
ANO 2021
PirSTAN 2021
SPD 2021
Přísaha 2021
KSČM 2021
ČSSD 2021
ČSSD 2017
ČSSD 2013
ČSSD 2010

Complete gallery of MrGreg's maps

Presidential elections

Volba 2018

Miloš Zeman
Černobíle
Jiří Drahoš
Černobíle

Volba 2013

Miloš Zeman
Černobíle
Karel Schwarzenberg
Černobíle

Legislative elections

Volby 2021

Volební účast
Rozdíl volební účasti
SPOLU
ANO
PirSTAN
SPD
Přísaha
ČSSD
KSČM

Volby 2017

Volební účast
Rozdíl volební účasti
ANO
ODS
Piráti
SPD
KSČM
ČSSD
KDU-ČSL
TOP 09
STAN

Volby 2013

Volby 2010

Volby 2006

Volby 2002

Volby 1998

Volby 1996

Volby 1992

Finland

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.

Kok 2011 (20.4%)
SDP 2011 (19.1%)
Kesk 2011 (15.8%)
PS 2011 (19.1%)
PS 2015 (17.7%)

Germany

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

CDU-CSU 2013
SPD 2013
Grüne 2013
Linke 2013
FDP 2013
AfD 2013
Piraten 2013
NPD 2013

CDU-CSU 2017
SPD 2017
AfD 2017
Grüne 2017
FDP 2017
Linke 2017
NPD 2017
Turnout 2017

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.

CDU-CSU 2009
SPD 2009
FDP 2009
Grüne 2009
Linke 2009
Piraten 2009

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

1990 Volkskammer election

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

NSDAP 1933, by User:Korny78 in 2007
NSDAP 1933, by User:Dove in 2008, re-colored by User:Furfur in 2015

Ireland (Republic of)

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

1921
1922
1923
Jun 1927
Sep 1927
1932
1933
1937
1938
1943
1944
1948
1951
1954
1957
1961
1965
1969
1973
1977
1981
Feb 1982
Nov 1982
1987
1989
1992
1997
2007
2011 (not used) [1]
2016 (not used) [2]
2020 (missing)

Ireland (Northern)

1973
1975 (Constitutional Convention)
1982
1998
2003
2007
2011
2016
2016 (by commons:User:沁水湾)
2017
2022

Made by User:RaviC:

Northern Ireland Conservatives in 2015

Japan

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

1942 Japanese general election: Taisei Yokusankai

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

Liberal Democratic Party, PR vote share 2021
Constitutional Democratic Party, PR vote share 2021
Nippon Ishin no Kai, PR vote share 2021
Kōmeitō, PR vote share 2021
Japanese Communist Party, PR vote share 2021
Democratic Party for the People, PR vote share 2021
Reiwa Shinsengumi, PR vote share 2021

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

Kazakhstan

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.

2021 Kazakh legislative election:

Korea (Republic of)

made by commons:User:沁水湾

Sim Sang-jung 2022 (2.38%), using 12 hues (!)

Netherlands

Areas where the Dutch Christian right Reformed Political Party (SGP) received a significant number of votes in 2010, largely co-extensive with the Dutch Bible Belt.
SGP 2003, using 5%-intervals (7 in total)

Nepal

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

Poland

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.

PO 2007
PSL 2007
PO+PSL 2007
PK 2007
Turnout 2007
Wahlkomitee in the Voivodeship of Opole

Portugal

CDU 2005 (jpg)
CDU 2005 (svg)
2019 Portuguese legislative election: parties to the left of PS (BE, CDU, LIVRE)
PS 2022 (de facto a party-specific chropleth map, except for Azores)

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:

Share of the Socialist Party (PS) by municipality
Share of the Social Democratic Party (PSD) by municipality
Share of CHEGA (CH) by municipality
Share of the Liberal Initiative (IL) by municipality
Share of the Left Bloc (BE) by municipality
Share of the Unitary Democratic Coalition (CDU) by municipality
Share of the CDS-People's Party (CDS-PP) by municipality
Share of the People–Animals–Nature (PAN) by municipality
Share of the Livre (L) by municipality

Scandinavia: Sweden, Norway, Denmark

Sweden

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.

(+) 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

Social Democratic
Moderate
Sweden Democrats
Green
Centre
Left
Liberal People's Party
Christian Democrats
Feminist Initiative
Shaded, red (S+V+MP) to blue (M+C+FP+KD)

Results of the 2018 Swedish general election

Social Democratic
Moderate Party
Sweden Democrats
Centre Party
Left Party
Christian Democrats
Liberals
Green
Shaded, red (S+V+MP) to blue (M+C+KD+L)

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

Votes by municipality as a scale from red/Left-wing bloc to blue/Centre-right bloc.
Votes by municipality as a scale from red/Red-green bloc to blue/Alliance for Sweden.

Feminist Initiative and Sweden Democrats:

FI 2014-6
FI 2014-9
SD 2002
SD 2006
SD 2010
SD 2014
SD 2018

Norway

2017 Norwegian parliamentary election.

Labour
Conservative
Progress
Centre
Socialist
Liberal
Christian
Green
Red

2021 Norwegian parliamentary election.

Labour
Conservative
Centre
Progress
Socialist Left
Red
Liberal
Green
Christian Democratic
Patient Focus

Denmark

Slovakia and others

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.

OĽaNO & allies 2020 (25.03%)
SMER-SD 2020 (18.29%)
Sme Rodina 2020 (8.24%)
ĽSNS 2020 (7.97%)
PS-SPOLU 2020 (6.97%)
SaS 2020 (6.22%)
ZĽ 2020 (5.77%)
MKS 2020 (3.91%)

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:

SMER-SD 2010 (18.29%)
SDKÚ-DS 2010 (15.42%)
SaS 2010 (12.15%)
KDH 2010 (8.53%)
Most-Híd 2010 (8.13%)
SNS 2010 (5.08%)
SMER-SD 2012 (44.42%)
KDH 2012 (8.82%)
SaS 2012 (8.56%)
Most-Híd 2012 (6.90%)
SDKÚ-DS 2012 (6.10%)
OĽaNO 2012 (5.88%)
SNS 2012 (4.56%)
SMER-SD 2016 (28.28%)
SaS 2016 (12.10%)
OĽaNO-NOVA 2016 (11.03%)
SNS 2016 (8.64%)
ĽSNS 2016 (8.04%)
Sme Rodina 2016 (6.63%)
Most-Híd 2016 (6.50%)
#SIEŤ 2016 (5.61%)
KDH 2016 (4.94%)

Other choropleth maps of elections in Slovakia found:

1935 Slovak provincial elections (by sk:User:Maros441)
DS 1946 (62% in Slovakia, 14% statewide)
KSČ 1946 (31% statewide)
HZDS 1992 (37.26%)
HZDS-RSS 1994 (34.97%)
2015 referendum (94.50% for man-woman marriage) (by sk:User:Belisarius~skwiki)
KDH 2019 (9.70%)

South Africa

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.

1994 General Election
1999 General Election
2004 General Election
2009 General Election
2014 General Election
2019 General Election

Turkey

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

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).

Servant of the People (SN) 2019 (43.16%)
Opposition Platform — For Life 2019 (13.05%)
Fatherland 2019 (8.18%)
European Solidarity 2019 (8.10%)
Voice 2019 (5.82%)
Turnout 2019

The first modern Ukrainian election per se:

1991 Ukrainian independence referendum

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:

Turnout 2002 (Rada)
Turnout 2006 (Rada)
Turnout 2007 (Rada)
Turnout 2012 (Rada)
Turnout 2014 (Rada)
Turnout 2019 (Presidential, 2nd round)
Kravchuk 1994, 1st round (38.4%)
Kravchuk 1994, 2nd round (45.2%)
Kuchma 1994, 1st round (31.8%)
Kuchma 1994, 1st round (52.4%)
KPU 1998 (24.65%)
Rukh 1998 (9.40%)
SPU-SLPU 1998 (8.56%)
Greens 1998 (5.44%)
NDP 1998 (5.01%)
Hromada 1998 (4.68%)
PSPU 1998 (4.05%)
SDPU(u) 1998 (4.01%)
Kuchma 1999, 1st round (36.49%)
Kuchma 1999, 2nd round (56.25%)
Symonenko 1999, 1st round (22.24%)
Symonenko 1999, 2nd round (37.8%)
Nasha Ukrayina 2002 (23.57%)
KPU 2002 (19.99%)
Kuchma's alliance 2002 (11.78%)
Tymoshenko's Bloc 2002 (7.26%)
SPU 2002 (6.87%)

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

Yushchenko 2004, 1st round (39.90%)
Yanukovych 2004, 1st round (39.26%)
Moroz 2004, 1st round (5.82%)
Yanukovych 2004, 2nd round
Yanukovych 2004, 2nd round re-run
Yushchenko 2004, 2nd round
Yushchenko 2004, 2nd round re-run
Yanukovych 2010, 1st round (35.32%)
Tymoshenko 2010, 1st round (25.05%)
Serhiy Tihipko 2010, 1st round (13.05%)
Yatseniuk 2010, 1st round (6.96%)
Yanukovych 2010, 2nd round (45.47%)
Yanukovych 2010, 2nd round (48.95%)

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

PR 2006 (32.14%)
Tymoshenko's Bloc (Fatherland+USDP) 2006 (22.30%)
Our Ukraine Bloc (NU+Rukh+KUN+others) 2006 (13.96%)
SPU 2006 (5.70%)
KPU 2006 (3.67%)
Vitrenko's Bloc (PSPU+Rus) (2.93%)

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%)	Bloc Yulia Tymoshenko results (30.71%	Our Ukraine People's Self-Defence results (14.15%)
Communist Party of Ukraine results (5.39%)	Bloc Lytvyn Party results (3.96%)	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%)	Bloc Yulia Tymoshenko results (30.71%	Our Ukraine People's Self-Defence results (14.15%)
Communist Party of Ukraine results (5.39%)	Bloc Lytvyn Party results (3.96%)	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

Scotland

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

2016 Conservatives (22.9%)
2016 Conservatives swing (+10.6%)
EU membership referendum Remain vote (62.00%)

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

2014 Scottish independence referendum "No" vote (55.30%)
Glasgow SNP 2017 (41.0%, 39)
Glasgow Labour 2017 (30.2%, 31)
Glasgow Conservative 2017 (14.6%, 8)
Glasgow Green 2017 (8.7%, 7)
West Lothian SNP 2017 (37.3%, 13)
West Lothian SNP 2022 (37.9%, 15)
West Lothian Labour 2017 (29.0%, 12)
West Lothian Labour 2022 (28.6%, 12)
West Lothian Conservative 2017 (23.2%, 7)
West Lothian Conservative 2022 (15.9%, 4)

United States

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:

1972 presidential election - Percentage of votes cast for John Schmitz by county
2016 presidential election - Percentage of votes cast for Gary Johnson by county
2016 presidential election - Percentage of votes cast for Jill Stein by county

Cities

Other interesting uses and types

Choropleth maps unrelated to elections

Poland's most denser gminy (by commons:User:Klarigi a.k.a. NerdyMaps)
Austria
Ukraine
Italy
Hungary
Switzerland
Germany
Belgium
The Netherlands
Central Europe

Multi-colored areas

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

Northern Ireland 1999
West Lothian 2007
Glasgow City 2007

Cartograms (anamorphosis)

2002 Cartogram with each municipality rescaled to the number of valid votes cast. The municipalities are the color of the party that got the most votes within the coalition that won relative majority.
2002 Cartogram of vote with each municipality rescaled in proportion to number of valid votes cast. Deeper blue represents a relative majority for the centre-right coalition, brighter red represents a relative majority for the left-wing coalition.
2006 Cartogram of the vote with each municipality rescaled in proportion to the number of valid votes. Deeper blue represents a relative majority for Alliance for Sweden, brighter red represents a relative majority for the Red-Green bloc.
Map showing the voting shifts from the 2002 to the 2006 election. Darker blue indicates a municipality voted more towards the parties that form Alliance for Sweden. Darker red indicates a municipality voted more towards the parties that form the red-green bloc.
2002 Votes by municipality as a scale from red/Left-wing bloc to blue/Centre-right bloc.

Various

commons:User:Magog the Ogre/Political maps