For this purpose, we used the data on NHSC participants and the data on non-participants from the first analytic dataset to estimate regression models in which we control for observable characteristics on each individual (Χᵢ), local area characteristics (Ζᵢ) and an indicator for program participation (Prog i)
We estimated model (1) by using the ‘same HPSA’ and the ‘any HPSA’ indicator variables as the dependent variable, respectively. The coefficient of interest, α, indicates the impact of NHSC program participation on the number of years served in a HPSA. The X vector included individual-level characteristics like age, gender and provider type, while the Z vector included Census division indicator variables and local area characteristics (at the zip code level), such as: the family income, poverty rate, percent White, percent Black, fraction of the population over 25 years of age with a high school degree and percent of the population over the age of 65. These variables helped control for factors that retain or induce providers to leave from their initial place of service.