Using quantile smoothing splines to identify employment subcenters in a multicentric urban area

The goal of this paper is to provide a statistically based definition of employment subcenters for multicentric urban areas. In particular, we examine the shape of the employment density function using quantile smoothing splines as a nonparametric empirical specification. This approach allows inspection of the employment gradient at the upper tail rather than the center of the employment density distribution. As a result, our definition of employment subcenters extends previous work as it allows us to condition on distance from the central business district, relies on the extent to which a subcenter influences surrounding areas, yet still emphasizes areas with high employment densities.