I'll probably dive into this more deeply over the coming week, but for now for CBRM:
Economic Region (Cape Breton Island) - stagnant (+/- 0%, +9)
CA (CBRM) - slight drop (-0.4%, -404)
CSD (CBRM) - slight drop (-0.6%, -591)
IR Eskasoni - increase (+2.9%, +99)
IR Membertou - increase (+8.7%, +88)
PC Sydney - increase (+2.6%, +790)
PC Glace Bay - decrease (-3.9%, -689)
PC Sydney Mines (aka Northside) - decrease (-3.7%, -470)
PC New Waterford - decrease (-9.3%, -693)
PC Eskasoni - increase (+9.5%, +223)
PC Howie Center - decrease (-4.4%, -51)
Current population of all Population Centers combined (within 15-20 minutes of downtown Sydney) 70,632.
I decided to look at the Population Center maps to see why Howie Center appeared to be removed from Sydney UA 2011 to make Sydney PC 2016, only to be added as it's own PC in 2021. Well, the maps are definitely weird.
Note the large swath of harbour in Sydney PC in South Bar,
the subdivision cut in half in Howie Center PC,
none of New Victoria included in New Waterford, among other decisions that appear to be a "coin toss" on the surface. The current maps make me wonder if there's a lack of local knowledge contributing to this, although much of the South Bar - Victoria Mines and Sydney River - Howie Center gaps where there appears to be a continuous population that should be included are larger lot properties (especially longer narrow lots in many of these areas, adding to land area more than population, reducing legal boundary population densities in these areas). The acreages on the Coxheath side have the same effect, though their of a more common acreage style than the narrow lot legacy of the Acadian property system on the island.