Trading on Time
利用98个国家货物从工厂到装船的天数数据，估计引力方程发现每延迟一天贸易减少超过1%，相当于平均距离增加70公里，对易腐农产品等时效性商品影响更大。
We determine how time delays affect trade, using newly collected data on the days it takes to move standard cargo from the factory gate to the ship in 98 countries. We estimate a difference gravity equation and find that each additional day that a product is delayed prior to being shipped reduces trade by more than 1%. Put differently, each day is equivalent to a country distancing itself from its trade partners by about 70 km on average. We also find that delays have a relatively greater impact on exports of time-sensitive goods, such as perishable agricultural products. © 2010 The President and Fellows of Harvard College and the Massachusetts Institute of Technology.