A model of human population motion

TL;DR

This paper presents a basic model of human mobility that distinguishes between short trips and relocations, highlighting the different time scales involved and contrasting recent empirical studies of human movement.

Contribution

It introduces a model capturing the distinct dynamics of trips and relocations, emphasizing the importance of multiple time scales in human mobility modeling.

Findings

Trips have characteristic time scales of months and days.

Relocations occur roughly on a yearly time scale.

Traditional models often assume a single mode of motion.

Abstract

We introduce a basic model for human mobility that accounts for the different dynamics arising from individuals embarking on short trips (and returning to their home locations) and individuals relocating to a new home. The differences between the two modes of motion comes to light on contrasting two recent studies, one tracking the geographical location of dollar bills \cite{brockmann}, the other that of mobile cell phones \cite{gonzalez}. Trips introduce two characteristic time scales; the time between trips, $\theta$, and the duration of each trip, $\tau$, and relocations introduces a third time scale, $T$, for the time between relocations. In practice, $T\sim{\rm years}$, $\theta\sim{\rm months}$, and $\tau\sim{\rm days}$, so the three time scales are widely separated. Traditionally, studies incorporating human motion assume only a single mode, using a generic rate to account for all types of motion.