When a new facility like a grocery store, a school, or a fire station is planned, the location should be determined by the necessity of people who live nearby.
We investigate the relation between the population density $\rho ({\bf r})$ and the facility density $D({\bf r})$ at the position ${\bf r}$ by proposing a simple model, and compare with empirical findings. We suggest that facilities in the private and the public economic sectors have different exponents $a \approx 1$ and $a \approx 2/3$, respectively, in $D \sim \rho^a$, which is explained in terms of the profit and the social opportunity cost.