Population is by city-proper. This explains the jump for Montreal, who expanded their borders in 2002, as well as nullifies the impact of Calgary's growth (considering Calgary's low amount of suburbs).
Thank you! Montreal expanded the city borders in 2002 and absorbed several other cities on the Island of Montreal (this in my eyes highlights one of the biggest downsides with using city proper population)
But that's alright, it's just an experimental chart for now!