5 Properties of Good Electoral Maps
Redrawing Sri Lanka’s Electoral Map
In Proportional Representation, First-Past-the-Post or Both, we discussed three alternatives to Proportional Representation (PR) — the Electoral System currently used in Sri Lankan General Elections.
We concluded with three questions, the first of which was,
“What would the Electoral Map look like if we returned to FPTP or adopted some mixed system?”.
Before we answer this question, we need to answer a meta-question, namely,
“What properties make a Good Electoral Map?”.
In this article, we discuss five such properties.
1) Population Balance
(and why we can’t use the existing Electoral Map)
The population of an Electoral District or Polling Division must be proportional to the seats assigned to it. We call this property “Population Balance”.
For example, Since Sri Lanka has about 20.3M people*, if our new EM has 160 electorates, each must contain about 130K people.
[*All population statistics quoted in this article are from the 2012 census.]
The current EM has significant differences in Population Balance.
At one extreme, the Kayts PD has 40K people. At the other extreme, the giant Nuwara-Eliya PD has 420K. If both PDs elected one MP, Kayts would have 10x as much representation (per capita) in parliament as Nuwara-Eliya.
Similarly, some EDs have a disproportionately larger or smaller number of PDs than the assigned seats.
If we assigned 160 seats across each ED in proportion to population, Jaffna ED (697K people) would get five seats, while Colombo ED (2.32M) would get 18. However, currently, Jaffna has 11 PDs, while Colombo has only 15. Hence, if we assigned one seat to each existing PD, Jaffna would have almost 2.5x as representation (per capita) as Colombo.
In other words, if we are to use First-Past-the-Post or a Mixed Electoral System, we need a new Electoral Map.
Population Balance is one of several properties that make a good Electoral Map. Let’s discuss some other important ones.
2) Contiguity
Travel from one point in a PD to another point in that PD should be possible without moving through another PD. In other words, the areas that make up a PD must be next to each other.
For example, the provinces of Sri Lanka are contiguous. The Colombo, Gampaha and Kalutara districts that make up the Western Province are next to each other — or contiguous. You can travel from Gampaha to Kalutara without travelling through (say) Matara.
Conversely, the Western Province would not be contiguous if it consisted of Kalutara, Colombo and Puttalam (and Gampaha was part of another district). Travelling from Colombo to Puttalam would necessarily involve travel through some other districts, not in the province.
Contiguity leads to both simpler maps and practical benefits. For example, with contiguity, a curfew enforced in a single PD would not inconvenience people in other PDs.
3) Respect for other Region Boundaries
Sri Lanka has many different regions and many different regional boundaries, which often form various region hierarchies.
For example, 9 Provinces, 25 Administrative Districts, 300+ Divisional Secretariat Divisions, and 14,000+ Grama Niladhari Divisions form a hierarchy of Administrative Regions. Similarly, the same 9 Provinces, 22 Electoral Districts, 160 Polling Divisions, and the same 14,000+ Grama Niladhari Divisions for a hierarchy of Electoral Regions.
Whenever we define a new region (as we will do when we define a new Electoral Map), it is preferable to respect the boundaries of existing regions.
For example, the 1978 Constitution that defined Electoral Districts (Eds) specified that they respect the boundaries of the existing 25 Administrative districts (ADs) in the following ways:
- An ED is the same as an AD. 20 EDs (all EDs except the Jaffna and Vanni) are equivalent to some AD.
- Or an ED is a combination of two or more ADs. The Jaffna ED combines the Jaffna AD and the Kilinochchi AD; the Vanni ED combines Mannar AD, Vavuniya AD, and Mullaitivu AD, or
- Or an AD is a combination of two or more EDs. As of now, no AD contains more than one ED)
[From now on, we will use the term “Old EM” to refer to the current electoral map and “New EM” to the new map we are designing. Similarly, Old EDs and Old PDs will refer to the Electoral Districts and Polling Divisions in the Old EM, and New EDs and New PDs, those in the new EM.]
When we draw our new EM, it would be preferable to respect the boundaries of the old EM. Hence, we would like to ensure the following:
- Always respect the boundaries of Old EDs. I.e. No new PD will split across more than one Old ED.
- Whenever possible, a new PD will be equivalent to some old PDs
- If not, a new PD is a collection of two or more old PDs. (Merge)
- If not, and old PD is split into two or more new PDs. (Split)
- If none of the above is possible (i.e. we cannot respect the boundaries of Old PDs), we will make sure that we respect the boundaries of GNDs, by making sure no Grama Niladhari Division (GND) splits across multiple PDs.
4) Respect for Ethnic, Religious and other groups
The design of an EM should not favour one group over another. Techniques such as Gerrymandering can achieve precisely this, which we must look to avoid.
We can verify (to some extent) if our new EM favours one group over the other by performing the following experiment:
Suppose some ED has two groups: A and B. Now suppose, everyone in group A votes for Party A, and everyone in B votes for Party B. Next, we look at how many seats Party A and Party B would get under proportional representation (PR) and how many seats would get under FPTP with our new EM for the ED. If the two numbers are the same or similar, we can conclude that FPTP with our new EM does not favour A or B.
Given the Sri Lankan context, it would be important the compare the following groups:
- Sinhala Buddhist (“Majority”) vs Everyone Else (“Minority”)
- Religious Groups — Buddhist, Hindu, Islam, Roman Catholic, Other Christian etc.
- Ethnic Groups — Sinhala, Tamil, Muslim + Malay, etc.
- Political Party affiliation.
Conversely, comparing the following groups would not be useful, given that differences across Sri Lanka are small.
- Gender
- Age Group
5) Compactness
Lastly, PDs with similar heights and widths (e.g. more like squares or circles) are preferable to those where the heights and widths differ significantly (e.g., narrow strips).
Like contiguity, compactness leads to both simpler maps and practical benefits.
The Next Article
In the next article, we will design and implement an “Electoral Map Mapping Algorithm” (EMMA) that will generate “Sri Lanka’s New Electoral Map” following these five properties.
Stay tuned!
[Disclaimer: I am a Computer Scientist, specialising in Artificial Intelligence, and no expert in Politic and Political Science. My interest in Sri Lankan Elections is purely one of a interested citizen and hobbyist.]
