Swiss Voting Patterns: Linear Projection with PCA

On the Swiss map below, each municipality is shown with a color that represents its voting habits as obtained by a linear projection through "principal component analysis" (PCA), from 1981 until today. Two municipalities with similar colors have similar voting habits, i.e., they are close to each other in the scatter plot. Observe for instance the differences between urban centers and rural areas, or between the different linguistic regions.

Explanation

On the scatter plot above, each municipality is shown by a dot. This representation is obtained directly from all the results to national-level referendum votes, using a dimensionality reduction technique called "principal component analysis" (PCA). On the Swiss map above, the color of each municipality is directly determined by its position in the two-dimensional scatter plot. Overall, two municipalities are close to each other in this space if they vote similarly. The axes of capture the topics and trends that most divided the municipalities during past votes. The first axis (horizontal) mainly represents themes associated to the openness of Switzerland, as well as social insurances. The second axis (vertical) mainly represents themes associated to transports, environment and agriculture. Below, we provide interpretations of these axes in terms of the most important votes that they represent.

Composition of the Axes

In the following tables, we show the most important votes represented by the two axes. The importance of each vote, illustrated on the right side of the list, indicates on which side of the axis the yes is located. If a vote has its importance directed to the right, it means that the municipalities that voted "yes" on this issue will tend to be represented on the right (for the horizontal axis), or at the top (for the vertical axis). Conversely, municipalities voting "yes" to a vote having its importance directed to the left will tend to be represented more on the left (for the horizontal axis), or at the bottom (for the vertical axis).

Horizontal Axis

Results Vote date Vote name Relative importance
2004-09-26 Change of the federal law on the income loss allowances for people serving in the military, civil service or civil protection (Allowances act for income loss)
100%
2004-09-26 Federal decree on the regular naturalization and the facilitated naturalization of second-generation young foreigners
97%
2013-03-03 Federal decree on family policies
96%
2004-09-26 Federal decree on the acquisition of nationality by third-generation foreigners
96%
1999-06-13 Federal law on maternity insurance
96%
2020-02-09 Amendment to the penal code and the military penal code (discrimination and incitement to hatred because of sexual orientation)
95%
2008-06-01 Popular initiative « For democratic naturalizations »
94%
1992-12-06 Federal decree on the European Economic Area (EEA)
94%
2001-03-04 Federal popular initiative 'Yes to Europe!'
93%
2017-02-12 Federal decree on simplified naturalization of foreigners of third generation
92%

Vertical Axis

Results Vote date Vote name Relative importance
1999-06-13 Federal Decree on the medical prescription of heroin
100%
1994-02-20 Federal decree on the continuation of the fee on heavy vehicles traffic
99%
1994-02-20 Federal law regarding the introduction of a fee on the traffic of heavy vehicles, related either to services or to the consumption,
97%
1994-02-20 Federal decree on the continuation of the national road tax
95%
1984-12-02 Federal decree on the popular initiative "on the compensation of victims of criminal violence"
93%
1992-05-17 Federal law on the protection of waters (Water Protection Act)
92%
1992-05-17 Federal decree for the introduction of a civilian service for conscientious objectors
89%
1992-05-17 Federal decree on the popular initiative "against the misuse of reproductive techniques and genetic manipulation to the human species"
88%
1994-09-25 Federal decree suppressing the reduction in the price of domestic wheat funded by tariffs of 18 March 1994
88%
2000-09-24 Constitutional article on an incentive fee on energy in favor of the environment (counter-proposal to the initiative 'Energy and Environment', which has been removed)
87%