One of the main aims of the regionalism and economic integration is to encourage export performance, especially intra-regional trade. The Constant Market Shares (CMS) method is commonly to examine empirically the countries' export performance. This paper is addressed to examine the regions' export performance by applying the CMS method. Firstly, this paper presents the developments of the method. Combining versions of the method by Leamer and Stern (1970), Richardson (1971a, 1971b) and Fagerberg and Sollie (1987), this paper comes up with another version of the method which, the competitive effect is explicitly extended. Second, the new version is then applied to analyze the dynamic markets of some regions (the EU, NAFTA, North East Asia and ASEAN) for the period 1980-2006. This paper concludes that the proliferation of regionalism and economic integrations in the beginning 1990-s caused the change in trade pattern. However, the change in trade pattern only happened in the short term.

• JEL Classification: F14, F15