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).
Vanni
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”.
Map Coloring
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.
Jaffna
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.
Batticaloa
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.
Digamadulla
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.
Kalutara
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.
Gampaha
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.
Moneragala
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).
Polonnaruwa
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.]
Trincomalee
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).
Matale
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).
Kegalle
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.
Matara
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.
