Both are related to a similar feature of modern production: the fact that it requires many complementary inputs. This includes not only raw materials and machines, which can be shipped around, but also many specialized labor skills, infrastructure, and rules, which cannot be moved easily and hence need to be spatially collocated.
这两个非常不同的不平等原因常常被混淆，导致两者都得不到清晰的思考。两种不平等于现代生产的相似特征有关：生产需要许多互补性投入。这些投入不但包括可从国外运输的原材料和机器，也包括许多专业化劳动技能、基础设施和规则，它们无法轻易转移，因此存在空间配置。缺少这些投入的任何一种，都可能对生产率带来灾难性影响。