This model simulates the population of the City of Toronto using a logistic (density-dependent) structure with three flows: births, deaths, and net migration. Births and deaths use roughly balanced constant per-capita rates, because Toronto's population is relatively young, a fact that continual immigration helps sustain. Net migration is the dominant driver of the city's real-world growth, and it's modeled as density-dependent: as the population approaches an estimated housing/land-constrained carrying capacity, net in-migration tapers toward zero, so growth slows and the population levels off rather than growing without bound.
