Centrality bias in inter-city trade
利用日本城市间贸易数据，发现中心大城市对其腹地的出口比引力模型预测高出50%–125%，这种偏差主要源于产业在中心城市的集聚及其对腹地的专业化供应。
Using Japanese inter-city trade data, we find a substantial centrality bias in aggregate gravity estimations: Shipments from large cities (central places) to their hinterland are 50%–125% larger than predicted by gravity forces. We argue that this discrepancy results from aggregating across industries , that concentrate in a few central places, which predominantly serve their respective hinterlands. Decomposing the centrality bias along the margins of our data, we attribute most of the centrality bias to substantially larger extensive industry margins in exports from larger cities to their smaller hinterland cities than vice versa.