Figure 2: Overall time of calls between residents of a county as a function of its population.
From: Urban characteristics attributable to density-driven tie formation
The points refer to the data (adapted from Calabrese et al.35 computed from ten million users’ mobile phone call records within United States during July 2010), while the solid line is the theoretical prediction from the model equation (5) adapted to raw population. The model captures both the super-linear growth and tilts on both ends of the curve while providing a superior fit to the data (based on adjusted R2-value) when compared with a pure power–law relation (dashed curve).
