Scale variance of the relationship between population and calling activity.
(a) Proportionality of call volume (CALLOUT) to population. Fits shown include linear trend (black), piecewise linear trend with an estimated structural break at 351 persons (red), and LOESS curve with 95% confidence intervals (blue). (b) Proportionality of call volume and population at larger geographic aggregations of size \(1\times1\) grid squares, \(2\times2\) grid squares, etc. LOESS curve fit to each separately with 95% confidence intervals. A 45 degree line (black) shows linear proportionality for comparison.