  We used a large database of 9 billion calls from 20 million mobile users to
examine the relationships between aggregated time spent on the phone, personal
network size, tie strength and the way in which users distributed their limited
time across their network (disparity). Compared to those with smaller networks,
those with large networks did not devote proportionally more time to
communication and had on average weaker ties (as measured by time spent
communicating). Further, there were not substantially different levels of
disparity between individuals, in that mobile users tend to distribute their
time very unevenly across their network, with a large proportion of calls going
to a small number of individuals. Together, these results suggest that there
are time constraints which limit tie strength in large personal networks, and
that even high levels of mobile communication do not fundamentally alter the
disparity of time allocation across networks.
