Quote from optioncoach:
Sorry but this still does not make sense. Not trying to be difficult but not sure why others do not find the logic questionable given the facts. If you have U.S. Dollars you do not need to "cash out", if you cash out you sell your dollars and then need to be in another currency. As of now you simply have dollars which you need to buy US Stocks. U.S. entities have dollars to go into the market and Foreigners have to convert to Dollars to get into the US stock market. If you are long the dollar then you do not have to sell the dollar to move it into the stock market like you have to unload a bond position to switch into stocks. Now traders might switch from trading forex to stocks but how many significant traders move back and forth between forex and stocks in enough regular size to affect the markets.
As for the correlation you might be looking at the past year alone where falling interest rates in the US have had some effect on pushing the markets up but weakens the dollar. If you look longer-term the correlation you mention does not really hold up.
In 2007 the SPX was essentially flat while the EUR/US went from like 1.3100 to 1.3400 and in 2005 the market was somewhat higher while the EUR/USD was down the entire year.
Nice trade if you went long but be careful when conjuring a rationale that does not make sense on the fundamentals.