"Voting with Their Feet": Delineating the Sphere of Influence Using Social Media Data

Delineating regional boundaries for places has a long tradition in geography, urban analysis and regional planning. Its theoretical basis may be traced back to the central place theory. The normative approach, using spatial interaction models, has been used, and the empirical approach, using commuting data, is also popular. While gathering commuting data using traditional methodologies (e.g., surveys) is costly, data capturing people’s locations and their thoughts, are widely available through social media platforms. This article demonstrates that Twitter data can be used to delineate boundaries among competing places. A generic approach based on the density of place names mentioned in geo-tagged tweets was proposed to reflect the sphere of influence or dominance of places. Locations with the same levels of influence from competing places constitute the boundaries delineating the regions dominated by the respective places. The method was tested to determine the boundaries between two metropolitan regions, two local cities, and two neighborhoods or communities. Results from these simple case studies demonstrated the validity of the general approach for evaluating existing place boundaries and determining boundaries if they have not been delineated. The method is applicable to different levels of the place hierarchy and has practical values for planning of places of different sizes.