Researchers Identify Laws Governing City Growth

Researchers have identified specific laws governing city growth that, they say, could help city planners and government peer into the future and plan accordingly.

While the growth or decline of a city may be the result of thousands of individual decisions made by those moving in and out of it, patterns exist that can be tracked, according to a study published in the Journal of the Royal Society Interface.

"People move for natural (e.g. disasters, climate change) or non-natural (e.g. volatile economic or social policies, wars) reasons," lead researcher Alberto Hernando of Ecole Polytechnique Federale de Lausanne said in a statement. "Being able to isolate and fit them into a model can help simulate and predict the impact that political or financial decisions can have in a region."

In coming to this conclusion, the researchers analyzed data records from the Spanish Statistics Institute (INE) from a period stretching from 1900-2011. A total of 45 million people across 8,100 municipalities in Spain were included in this information.

Based on their analysis, a city's future growth is largely influenced by its past growth so long as it is home to at least 10,000 people, the study found. Furthermore, at least 15 years of population data is needed in order to obtain the best results.

A second major factor in a city's growth is that of neighboring cities, particularly when they are within 80 kilometers of one another. The farther the cities, the weaker the relationship.

Given the model's success, Hernando hopes to extend it so as to further isolate factors influencing people's decisions to move, as well as forecas the growth of commercial companies based on changes in their value.

"Our long-term goal is to develop a simulation tool including all demographic, social, and economic forces in scene, where virtual copies of cities grow and develop in hypothetical situations, mimicking the response of their real-world counterparts."