1.介绍了经济增长速度、收入差距、区域差距、城市集聚、人口出生和死亡率5个方面的倒U型事实。分析了这5个方面的相互作用。
2. 分析了各个指标达到倒U顶点的顺序
城市化的集中与区域差距。It  is  my  impression that  the  crest  of  geographic concentration occurs earlier than  that  of regional inequality, which is earlier than  that of  economic  growth.
收入差距与区域差异。One  may  also  speculate  that  the  crest  of  social  inequality  may  more  or  less coincide with the  reduction  of regional  inequality.
可能的缺陷
发展是一个立方体，其涉及到经济、社会、文化、政治、环境等等方面。文章涉及到的仅仅5个方面而已。环境、民主有可能是倒U的。

另一篇相关文献在此：https://bbs.pinggu.org/thread-3048700-1-1.html
Amos Orley M. Unbalanced regional growth and regional income inequality in the latter stages of development [J]. Regional Science and Urban Economics, 1988, 18(4), 549–566.

研究对象：1969-1983年美国50个州
指标：人均收入
区域差距演化：50个州中有37个呈现“增长——下降——增长”的模式，而不是“增长——下降”倒U模式。
原因：郊区化、服务型经济的发展。
这篇文章的一大看点：综述写的相当好

再一篇 地址：https://bbs.pinggu.org/thread-2554188-1-1.html
Garrido-Yserte R, Mancha-Navarro T. The Spanish regional puzzle: Convergence, divergence and structural change [A]. In: Cuadrado-Roura JR (ed). Regional policy, economic growth and convergence [M]. Berlin: Springer, 2010.

相关研究困境
Nowadays, the analysis of regional disparities continues to be of great interest to professional economists and geographers, as well as to those dedicated to the design and implementation of regional development policy. This need for analysis is due to the lack of a unified sole theoretical response regarding the evolution of regional economic disparities and the need to demonstrate under which circumstances these disparities tend to diminish.

主题：生产率差距缩小，而生产活动聚聚
This chapter attempts to answer the Spanish Regional Puzzle: How is it possible to combine convergence in relative terms, particularly significant in the case of productivity, with an increase of divergence in the most important absolute variables: gross value added (GVA), employment and population?

研究对象
西班牙的各个区域，1986-2006年

答案：第三产业的发展
The answer lies in regional structural change. The important tertiarisation process of the Spanish economy in these years has caused regional productivity levels to reduce their differences, although at the expense of a greater difference in the distance between the most- and the least-developed regions, with regard to their participation in GVA and employment.