# Effects of the distant population density on spatial patterns of demographic dynamics

## TL;DR

This study investigates how individuals in Japan consider distant population densities when making migration decisions, revealing that local perceptions influence demographic dynamics more than traditional gravity models suggest.

## Contribution

The paper introduces an extended gravity model incorporating local population density averages to better explain migration patterns.

## Key findings

- Population growth correlates with nearby and local population densities.
- Standard gravity models fail to capture empirical migration behaviors.
- Extended models with local density perception improve fit to data.

## Abstract

Spatiotemporal patterns of population changes within and across countries have various implications. Different geographical, demographic and econo-societal factors seem to contribute to migratory decisions made by individual inhabitants. Focussing on internal (i.e., domestic) migration, we ask whether individuals may take into account the information on the population density in distant locations to make migratory decisions. We analyse population census data in Japan recorded with a high spatial resolution (i.e., cells of size 500 m $\times$ 500 m) for the entirety of the country and simulate demographic dynamics induced by the gravity model and its variants. We show that, in the census data, the population growth rate in a cell is positively correlated with the population density in nearby cells up to a radius of 20 km as well as that of the focal cell. The ordinary gravity model does not capture this empirical observation. We then show that the empirical observation is better accounted for by extensions of the gravity model such that individuals are assumed to perceive the attractiveness, approximated by the population density, of the source or destination cell of migration as the spatial average over a radius of $\approx 1$ km.