英文文献：An Efficiency Analysis of Nevada and Utah Counties: Region Size Leads Regional Efficiency
英文文献作者：Kim, Man-Keun,Harris, Thomas R.
英文文献摘要：
The hypothesis that regional size increases regional efficiency is tested in this study. Data Envelopment Analysis and the Directed Acyclic Graph were used to reveal the causal relationship between regional efficiency and region size in terms of population density. Region size and the infrastructure directly cause regional efficiency, and regional efficiency affects regional income indirectly via formulation of Metropolitan area