Many East Asian countries have shifted from pegging their currency to the US dollar to targeting a basket of currencies, including Asian currencies, by the late 1990s. This shift was not due to common shocks or market forces, but rather a deliberate move towards fixed exchange rates. The researchers used a method called Markov-switching estimation to analyze this shift and found that most countries in the region have stuck to fixed exchange rates. This suggests the existence of a de facto Asian Currency Unit bloc in East Asia.