Figure 1

Mobile phone user statistics. The main figure shows the population pyramids for the egos (filled bars) and alters (unfilled bars) showing the relative frequencies for each gender and age group. The upper inset shows the relative frequency histogram of the age difference among the pairs considered, while the lower inset shows the relative frequency histograms of the egos’ moving months, with the composition by age group indicated by the stacked bars. Due to the requirement that the ego and alter must be active for four months before and after the moving month, none of the egos in our analysis moved before May 2008 or after August 2009