Demographics module

Motivation for inclusion. To accurately describe the characteristics and dynamics of our specific context we need to ensure that the population in our model is representative of this context. For our model, we want racial, spatial, age, and HIV status distributions to follow those observed among MSM in Chicago.

Means of inclusion and data sources. Our starting point is the numbers of males aged 13 to 70 years in the Chicago census data by race/ethnicity. Based on the AIDSVu [43] MSM estimates of 6.6% of males in Cook County aged 13 to 80 years old, we calculated a total of approximately 65,000 MSM living in Chicago. As detailed local data is missing, our model assumes that the proportion of MSM is constant across race/ethnicity and age. To reduce computational requirements, the LHM samples 10% of this population (6500 individuals), describing the city on a 1:10 scale while maintaining the race/ethnicity, age, and location data from the Chicago census, and HIV prevalence distributions using demographic conditions from CDPH surveillance data.

The population size in the model will fluctuate over time. Model dynamics account for individuals who die (both due to natural causes and to HIV) at rates based on local data for non-HIV and HIV-related mortality and for individuals aging out of our model’s age range or entering our model as they become of age. Our model does not account for in or out migration as this factor was not notable; inflow and outflow were roughly equal in our model, keeping the total population around 6500 throughout the simulation.