In an attempt to make the changes between 2011-2015 easier to grasp, I plotted out the boundaries on Google Maps then did screenshots to create animated gifs.
I’ve just chosen 3 constituencies for the exercise: Ang Mo Kio, Bishan-Tao Payoh, and Marine Parade.
Marine Parade is the easiest to understand. Essentially, in 2015, it ate up the former Joo Chiat SMC and part was hived off to create MacPherson SMC. Although this resulted in a net increase in area, the number of voters dropped. MacPherson is a densely populated HDB heartland. Joo Chiat has more landed property.
Ang Moh Kio saw a similar change but in reverse: it got smaller by area but the population increased. The big chunk it lost along Upper Thomson Rd, which is a lot of landed property, went to Nee Soon. The small bits it gained in 2015 were two HDB estates: one, a tiny piece of Sengkang West SMC and the other, in Hougang, was a small corner of Pasir Ris-Punggol GRC in 2011.
Bishan-Toa Payoh was the most interesting story because of all the changes in the neighbouring area. It almost doubled in size eating up a piece of the former Moulmein-Kallang GRC. A lot of what it didn’t eat ended up in the new Jalan Besar GRC, with spare bits going to Tanjong Pagar and Holland-Bukit Timah. Overall the actual size in terms of voters in Bishan-Toa Payoh did not increase in line with the area as most of that gain was parkland.