Many ASEAN countries have trade-to-GDP ratios as well as trade-intensity ratios (which normalize bilateral trade by the relative share of the countries in total world trade to eliminate size effects) that are higher than in Western Europe (Goto and Hamada 1994, Kawai and Takagi 2000). At close to 25 percent, the share of intraregional trade in ASEAN total trade, although lower than in the EU (40 percent), is significant and rising (Bayoumi and Mauro 1999). It is much higher than in some of the other currency unions such as the Eastern Carribean Currency Union (about 10 percent), the Western Africa Economic and Monetary Union (about 10 percent), and the Central African Economic and Monetary Community (about 3 percent). Although there are intercountry differences, the symmetry in shocks among the countries in the region is comparable to the EU (Eichengreen and Bayoumi 1999). The regionwide economic slowdown in 2001 in response to the global economic downturn is another evidence of the high degree of shock symmetry among these countries. The high degree of shock symmetry reflects both the high degree of openness (export orientation, capital flows etc.) and the similarities in the production structures among these economies.