For example, the city of Vancouver has a smaller population than Edmonton or Mississauga, but is far more important internationally. It just happens to be a "city" made up of many cities, unlike Edmonton which happens to have most of its population within one city boundary. If Vancouver, Burnaby, and Surrey were to amalgamate, it would make very little difference.
Similarly, Nanaimo has a larger population than the City of Victoria, despite Victoria being a population centre of about 4x the size. It just so happens to be the hub of the built up area of 13 municipalities. Few people would think of Victoria as being smaller than Nanaimo. In fact, Saanich, a suburb of Victoria, is actually more populated than Victoria itself.
50% of Canada'a population lives below the red line