The New Electoral Map of Sri Lanka
In How to Draw Sri Lanka’s New Electoral Map, we discussed the workings of an Electoral Map Mapping Algorithm (EMMA).
As we saw, EMMA takes the Old Electoral Map of Sri Lanka as input. It modifies it step-by-step, gradually making it more and more optimal in terms of the five properties proposed in “5 Properties of Good Electoral Maps”. Once “sufficiently optimal”, EMMA outputs the New Electoral Map.
In this article, we will look at EMMA’s output.
Before we proceed, let’s look at two assumptions that we’ve made.
Electoral Map with 160 Polling Divisions each with one seat
EMMA generates an Electoral Map dividing Sri Lanka into 160 Polling Divisions, each with one seat. Since EMMA respects Electoral District (ED) boundaries, these 160 seats are first allocated amongst the 22 Electoral Districts.
The seats allocated by EMMA to each ED differs from the 2020 (and other) Parliamentary Election Allocations because EMMA allocates only 160 seats to the EDs, while in Parliamentary Elections, 196 seats are allocated (of which 160 are allocated proportionally and 36 based on province, somewhat disproportionally).
Population vs Registered Voters
EMMA allocates seats proportional to population, while in Parliamentary Elections, the 160 seats allocated proportionally are allocated in proportion to the number of registered voters.
EMMA uses population (from the 2012 census) because it needs population data at the Grama Niladhari Division (GND) level. As of now, we don’t have access to registered voters at this level. Hence, EMMA cannot use registered voters for proportional allocation.
Compared to the Parliamentary Elections allocation, EMMA’s allocation is likely to favour populations a smaller proportion of registered voters — i.e. those with younger populations.
Assumptions out of the way, we will now discuss EMMA’s results grouped by the strategies it uses to modify the Old Electoral Map (How to Draw Sri Lanka’s New Electoral Map describes these strategies in detail).
Do Nothing (1 ED)
The Vanni ED is assigned 3 seats, and conveniently it currently has 3 PDs.
As we discussed in 5 Properties of Good Electoral Maps, “Since Sri Lanka has about 20.3M people (2012 Census), if our new EM has 160 electorates, each must contain about 130K people.”. 130K is the ideal. A PD which has slightly larger or smaller would be sufficient for “Population Balance”.
The shading on the map below (and all the maps on this article) indicates the level of population balance. Shades of blue indicate that the PD has more seats relative to its population, or equivalently a smaller population relative to its seats. Shades of red indicate the opposite.
While none of the Vanni PDs has an ideal population, none diverges too much either. EMMA chooses to “Do Nothing” and re-use the old PDs in the new Electoral Map.
We could use the “Merge and Split” strategy to achieve an even better population balance, but this would be at the expense of respecting Old PD boundaries. EMMA favours the latter, but there is no “scientific” way to manage this tradeoff.
Merge Only (1 ED)
The Jaffna ED is assigned 5 seats, and has 11 PDs on the current Electoral Map. As expected there are many “blue PDs” with populations smaller than the Ideal PD.
Hence, EMMA “merges” the following groups of PDs into larger PDs:
- Jaffna and Nallur
- Kopay and Kankesanthurai
- Manipay, Vaddukoddai and Kayts
- Point Pedro, Chavakachcheri, and Udupiddy
The remaining Kilinochchi PD is left unchanged.
Split Only (4 EDs)
The Batticaloa ED is assigned 4 seats, and has 3PDs on the current Electoral Map. The Batticaloa and Kalkudah PDs are roughly the correct sizes (“colourless”), while the Paddiruppu PD is approximately 2x the ideal size (“dark red”).
Hence, EMMA splits Paddiruppu into two PDs, into Paddiruppu-North and Paddiruppu-South. Following this split, Batticaloa is almost “colourless” — i.e. all its PDs are fairly well balanced.
The Digamadulla ED is assigned 5 seats, and has 4 PDs on the current Electoral Map. The largest of these is Ampara which is about 1.6x the ideal side (“fairly red”).
Like Paddiruppu in Batticaloa, EMMA splits the Ampara PD into two PDs: Ampara East and Ampara West.
The Kalutara ED is assigned 10 seats, and has 8 PDs on the current Electoral Map.
EMMA splits the largest two of these, Panadura PD and Horana PD, into Panadura North, Pandora South, Horana East and Horana West.
The Gampaha ED is assigned 18 seats, and has 13 PDs on the current Electoral Map.
The shortfall of 5 PDs is closed by splitting the largest 5 PDs (Katana, Mahara, Ja Ela, Gampaha and Biyagama) each in two. Hence, these are replaced by Katana North and Katana South, Mahara East and Mahara West, Ja Ela North and Ja Ela South, Gampaha East and Gampaha West, and, lastly, Biyagama East and Biyagama West.
Merge and Split (6 EDs)
The Moneragala ED is assigned 3 seats, and has 3 PDs on the current Electoral Map. The Moneragala PD is roughly the correct size. Bibile is slightly too small, while Wellawaya is about 1.6x the ideal size.
If Bibile and Wellawaya were contiguous, EMMA could have merged them, and then split them more equitably. However, this is not the case with the Moneragala PD getting in the way. Hence, EMMA merges all three, and then splits them into three more equal sized PDs. The Moneragala PD is split into Moneragala North (containing the old Bibile PD, and parts of the Moneragala PD), Moneragala South East and Moneragala South West (both containing parts of both the old Moneragala and Wellawaya PDs).
Like the Moneragala ED, the Polonnaruwa ED is assigned 3 seats, and has 3 PDs on the current Electoral Map. Like the Wellawaya PD in the Moneragala ED, the Polonnaruwa PD in the Polonnaruwa ED is about 1.6x the ideal size. Unlike , Wellawaya, the Polonnaruwa PD is next to Medirigiriya PD, which is slightly smaller than the ideal.
Hence, instead of merging three PDs, and splitting them back into three new PDs, we can merge just two PDs, and split them more equitably. Hence, we merge the Polonnaruwa and Medirigiriya PDs, and split them to form Polonnaruwa-Medirigiriya North (contianing the old Medirigiriya PD and part of the Polonnaruwa PD) and Polonnaruwa-Medirigiriya South (containing the rest of the old Polonnaruwa PD). The original Minneriya PD is preserved.
[We will name the new PD by the merged PDs (e.g. Polonnaruwa-Medirigiriya) and the direction of splitting (e.g. North, South). This can result in long cumbersome names, and should be renamed to more convenient ones.]
Like the Moneragala ED and Polonnaruwa EDs, the Trincomalee ED is assigned 3 seats, and has 3 PDs on the current Electoral Map. Similar to the Wellawaya PD in the Moneragala ED, and the Polonnaruwa PD in the Polonnaruwa ED, the Seruvila PD is about 1.5x the ideal size. Like the Polonnaruwa PD, it is next to the much smaller Muttur PD.
Hence, EMMA merges Seruvila and Muttur, and then splits them more equitably into Muttur-Seruvila North and Muttur-Seruvila South (each containing parts of both the old Muttur and Seruvila PDs).
The Moneragala ED is assigned 4 seats, and has 4PDs on the current Electoral Map. Like the EDs discussed above, it has a small PD (Laggala) and a large PD (Dambulla) next to each other.
EMMA merges and splits the two into Laggala-Dambulla South (containing the old Laggala PD and part of Dambulla PD), and Laggala-Dambulla South (containing the remainder of the old Dambulla PD).
The Kegalle ED is assigned 7 seats, and has 9 PDs on the current Electoral Map.
EMMA leaves Yatiyantota and Deraniyagala unchanged. It merges Ruwanwella, Dedigama and Galigamuwa, and splits the resultant area into 2 PDs: R-D-G* North (containing parts of the old D and G PDs) and R-D-G South (containing parts of all three PDs).
[For clarity, we’ll use this abbreviated form. However, if these new PDs are to be used in practice, we must appropriately rename them.]
Similarly, Kegalle, Rambukkana, Aranayaka, and Mawanella are merged into 3 PDs: K-R-A-M North, K-R-A-M South West, and K-R-A-M South East.
EMMA favours “population balance” over respecting old PD boundaries in Kegalle, by doing 2 fairly complex Merge and Split operations. More simpler modifications would have left more PD boundaries intact, at the cost of poorer population balance.
The Matara ED is assigned 6 seats, and has 7 PDs on the current Electoral Map, and hence has one PD too many.
One obvious strategy might have been to pick the smallest PDs, Devinuwara and Kamburupitiya (which happen to be next to each other) and merge them. However, with 198K people, the resulting PD is about 1.6x the ideal size or quite big.
Hence, instead, EMMA chooses to merge Devinuwara and Kamburupitiya with the Matara PD, the split the resulting area more equitably into M-K-D North and M-K-D South.
EMMA applies various combinations of the above strategies to the remaining 10 EDs. We will consider them more briefly.
Various Combinations of Merge, Split and Merge and Split (10 EDs)
9 old PDs. 6 new seats.
- (-1 net change of PDs) Viyaluwa and Passara are merged into Viyaluwa-Passara.
- (-1) Hali Ela and Badulla PD are merged into Hali-Ela-Badulla
- (-1) Welimada, Uva Paranagama and Haputale are merged and split into W-U-H North (containing all of the old Uva-Paranagama and part of Welimada) and W-U-H South (containing all of Haputale, and the remainder of Welimada).
- (0) Mahiyanganaya and Bandarawela remain unchanged.
4 old PDs. 5 new seats.
- (+1) Thissamaharama is split into Thissamaharama East and Thissamaharama West.
- (0) Beliatta (small) and Tangle (large) are merged and split into the more balanced Beliatta Tangalle West (containing all of the old Beliatta and some of Tangalle) and Beliatta Tangalle East (containing the rest of Tangalle).
- (0) Mulkirigala remains unchanged.
7 old PDs. 7 new seats.
- (+1) The large Mihintale PD is split into Mihintale North and Mihintale South.
- (-1) Anuradhapura West, Anuradhapura East and Medawachchiya (all “blue”) are merge and split into 2 larger PDs: A-A-M North and A-A-M South*.
- (0) Horowpothana, Kalawewa, and Kekirawa remain unchanged.
[* As I said earlier, netter names are needed.]
5 old PDs. 6 new seats.
- (+1) The big ED Chilaw, is split into Chilaw North and Chilaw South.
- (0) Puttalam and Anamaduwa are merged and split for better balance.
- (0) Nattandiya and Wennappuwa remain unchanged.
4 old PDs. 6new seats.
- (+4) The giant Nuwara-Eliya Maskeliya PD is split into 4 PDs: Nuwara-Eliya-Maskeliya East North, East South, West North and West South*.
- (-1) Kothmale, Hanguranketha, and Walapane are merge and split into 3 PDs.
[* The strange names result from the order EMMA split the original PD: first West-East, then North-South. As mentioned before, better names are needed.]
8 old PDs. 9 new seats.
- (+1) The largest PD Eheliyagoda is split Eheliyagoda West and Eheliyagoda East.
- (0) The adjacent Kalawana (small) and Kolonna (large) PDs are merged and split into Kalawana-Kolonna West (containing all of Kalawana and part of Kolonna) and Kalawana-Kolonna East (containing the rest of Kolonna) for more balance.
- (0) Pelmadulla (small) and Nivithigala(large) are also merged and split into Nivithigala-Pelmadulla North and Nivithigala-Pelmadulla South, each containing parts of both original PDs.
- (0) Balangoda, Rakwana and Ratnapura PDs remain unchanged.
10 old PDs. 8 new seats.
- (-1) Balapitiya and Karandeniya are merged into Balapitiya-Karandeniya.
- (-1) Galle PD, Ratgama and Ambalangoda, are merged and split into G-R-A West (containing all of the original Ambalangoda and part of Ratgama) and G-R-A East (containing the rest of Ratgama and all of the original Galle PD).
- (0) Baddegama (large) and Hiniduma (small) are merged and split into Baddegama-Hiniduma North (containing all of Hiniduma and part of Baddegama) and Baddegama-Hiniduma South (containing the rest of Baddegama).
- (0) Akmeemana, Bentara-Elpitiya and Habaraduwa remain unchanged.
13 old PDs. 11 new seats.
- (-1) Senkadagala and Hewaheta are merged into Senkadagala-Hewaheta
- (-1) Ududumbata and Teldeniya are merged into Ududumbata-Teldeniya
- (0) Nawalapitiya (large) and Gampola (small) are merged and split into Nawalapitiya-Gampola South and Nawalapitiya-Gampola North, each containing parts of both original PDs.
- (0) Harispattuwa (large) and Galagedara (small) are merged and split into Harispattuwa-Galagedara South and Harispattuwa-Galagedara North, each containing parts of both original PDs.
- Kundasale, Mahanuwara, Pathadumbara, Udunuwara and Yatinuwara remain unchanged.
14 old PDs. 13 new seats.
- (-1) Panduwasnuwara and Wariyapola are merged into Panduwasnuwara-Wariyapola.
- (0) Kurunegala (large) and Mawathagama (small) are merged and split into Mawathagama-Kurunegala North and Mawathagama-Kurunegala South, each containing parts of both original PDs.
- (0) Bingiriya, Dambadeniya, Dodangaslanda, Galgamuwa, Hiriyala, Katugampola, Kuliyapitiya, Nikaweratiya, Polgahawela, and Yapahuwa remain unchanged.
Finally Colombo. 15 old PDs. 18 new seats.
- (+1) Kaduwela is split into Kaduwela East and Kaduwela West.
- (+1) Kesbewa is split into Kesbewa North and Kesbewa South.
- (+1) Homagama is split into Homagama North and Homagama South.
- (+1) Maharagama is split into Maharagama West and Maharagama East.
- (-1) Dehiwala, Kotte and Colombo East are merged and split into D-K-C South and D-K-C North, each containing parts of all three original PDs.
- (0) Colombo West (small) and Colombo Central (large), are merged and split into Colombo West-Colombo Central North and Colombo West-Colombo Central South.
- (0) Ratmalana (small) and Moratuwa (large), are merged and split into Moratuwa-Ratmalana North (containing all of the original Ratmalana PD, and some of Moratuwa) and Moratuwa-Ratmalana South (containing the rest of Moratuwa).
- (0) Borella (small) and Kolonnawa (large) are merged and split into Borella-Kolonnawa East and Borella-Kolonnawa West, each containing parts of both original PDs.
- (0) Avissawella and Colombo North remain unchanged.
How EMMA did relative to the “5 Properties”
1) Population Balance
In 5 Properties of Good Electoral Maps we noted that the population balance of the current Electoral Map was particularly poor. (“At one extreme, the Kayts PD has 40K people. At the other extreme, the giant Nuwara-Eliya PD has 420K”).
In contrast, EMMA’s the new electoral map is far more balanced and “colourless”.
There are still some imbalances, but we saw how these were made in the interest of other tradeoffs like repecting old PD boundaries.
All the new PDs were contiguous.
3) Respect for other Region Boundaries
In a few places, EMMA opted for population balance over “Respect for other Region Boundaries”, but in other places were opted for the reverse tradeoff.
Of the 160 PDs in the new electoral map, 64 were unchanged from the old map, 10 PDs resulted from merging one of more old PDs, 38 resulted from splitting old PDs.
Hence, 112 of the 160 PDs (or 70%) respected old PD boundaries.
The remaining 48 new PDs that cut across PD boundaries still respected Grama Niladhari Divisions (GND) boundaries by design.
4) Respect for Ethnic, Religious and other groups
See Next Steps.
Compactness is a somewhat subjective and aesthetic quality. I’ll leave it to you (dear reader) to inspect the maps of the new PDs, and comment on this further.
We will discuss “Respect for Ethnic, Religious and other groups” in a future article, as it is both controversial and interesting.
Similarly, we will also discuss the effect of this new Electoral Map on political parties, and the results of previous elections.
[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 an interested citizen and hobbyist.]