Well in such countries like india, other asian countries which are developing and have chances for better income, foreign investors coming with their money and making investments. Because they can get better income with their money in developing countries. But in case of a crisis in their own countries they are taking their money back from investing in foreign countries. (Not only in developing countries, even in Europa they are taking their money from financial sector) And the currency that they want is USD which is used in their countries. So while they are collecting their money from their investments, it starts to be high demand on USD which makes USD to become valuable in other currencies. Sorry for my bad English, hope I could explain it with my poor English :)