This deterministic model explores how Durham Region's human population could change over 100 years from an illustrative baseline of 800,000 residents. Population is the stock, measured in people. Births and Inmigration add people; Deaths and Outmigration remove people. All four flows are measured in people per year. As the population grows, pressure on housing and services reduces inmigration. A two-year response delay represents the time between changing conditions and decisions to move. This creates a balancing feedback that gradually slows growth.
Assumptions: birth rate = 0.010/year, death rate = 0.008/year, outmigration rate = 0.005/year, maximum potential inmigration = 40,000 people/year, and hypothetical housing/service capacity = 2,000,000 people. Actual inmigration is the maximum inflow multiplied by the available capacity fraction, bounded below by zero. Capacity influences migration; it is not a fixed biological ceiling.
At year 0, births = 8,000, deaths = 6,400, inmigration = 24,000 and outmigration = 4,000 people/year. Net growth is therefore 21,600 people/year (2.7%). The stock accumulates births + inmigration - deaths - outmigration.
Click Simulate to view population, annual flows and a numerical table. Select a component to read its equation, units and explanation. Sliders allow experiments with migration, demographic rates, capacity and delay. Time is in years from the baseline; the numerical time step is 0.25 years.
The starting population is rounded as suggested in the assignment. All other inputs are illustrative assumptions, so this is a scenario model rather than an official forecast. It omits age structure, changing policies, new housing construction and random shocks. Adapted from Bob Bailey's logistic moose example, with separate human demographic flows and delayed migration feedback.