After a long period of pegging the Chinese yuan to the US dollar at about 6.1-to-1, China devalued the yuan in a sneak attack on August 11, devalued again Wednesday & Thursday. The total devaluation is almost 5%, the biggest devaluation in over 20 years. Normal daily volatility in foreign exchange markets is measured in 5 decimal places. 0.05% is a choppy day. 5.0% is an earthquake.