Is the yen a negative beta asset?

Here is an intriguing graph I ran across recently. The blue line is FXY, an exchange-traded fund that tracks the yen. The red line is the S&P 500 index. Over the past year, the two time-series look like mirror images of each other. That is, holding yen seems to hedge U.S. stock-market risk.

Update: John Campbell, the smartest finance economist I know, offers me this explanation:

Why the striking pattern in the last year? I think it's because during the liquidity crisis, the stock market has fallen at times when hedge funds and investment banks are deleveraging -- at such times, they cover the carry trade, that is, they buy yen and sell high-interest currencies such as the Australian dollar.

That story is consistent with the increasing risk of the carry trade.