作者：Shen Hao/ Li Huanyu

Abstract:Through the enlargement of EU towards a new stage, which has accepted some underdeveloped members, some concerns have been raised in this topic: whether these center countries could harmonize with these peripheral countries. This paper demonstrates related background, such as similar Bretton Woods System and the current process of EU. After that, it analyzes the advantages and disadvantages of core and peripheral countries based on their economic traits respectively.  And than we analysis the affects of this mode on the labor mobility at two different speeds.  At last, we conclude that a much broader EU is beneficial for the whole Europe and the world economy.