Michael Turton does a good analysis on districts in terms of voting population, which is the figure you'd be looking at if you were gerrymandering. He points out that the number of seats per county seems to favor Taoyuan and Taipei County disproportionately, and should the CEC have been more favorable to the DPP, could have given Tainan and perhaps Kaohsiung another seat while cutting something from Taipei County or Taoyuan.
Of course, the CEC is drawing districts that are largely contiguous and along established county/township lines (there are some exceptions in Taichung, especially). Another goal was to keep communities with common interests together -- hence dividing Yunlin and Miaoli into coastal and interior districts, as both the political leaning and economic interests of these voters differs along these geographic lines. Remember, the average number of voters per county is 230,000 ...
Now if we rank these counties by total population size, which is what the CEC has to work with, we get the following result, where five of the counties with largest population were green, and five were blue:
- Hsinchu County (projected independent)
- I-lan County (projected green)
- Taichung City-2
- Tainan County-3
- Tainan City-1
- Keelung City
- Tainan City-2
- Taipei City 4 (competitive)
- Tainan City-4
- Tainan County-2
Most Taipei County, Kaohsiung and Taoyuan seats fall right in the middle of the range of size, with between 250-300,000 voters in each seat.
But if we do a comparison, we do indeed see a relative marginalization of the Tainan voters:
Taipei County averages 283K citizens/seat; Taoyuan, 312; Kaohsiung, ; and Tainan, 372, while a 6th seat in Tainan would have yielded a much more similar 310K/seat.
Still, sometimes you get what you wish for, right?