Because, we are buying more foriegn goods, mostly. It also helps that a lot of people are borrowing money and not paying it back quickly. What this does is "create" American money in the world-wide market, and when there is more money going around per person it becomes worth less, causing the international value to go down.

__________________
"If I didn't live in Ohio I would love to live in Texas, it's the only place where drinking beer and kickin' ass is still accepted." -Roman