Investors should be at least a little concerned by recent weakness in an exchange traded fund pegged to the Australian dollar since the currency has been a fairly reliable leading indicator for U.S. stocks.

CurrencyShares Australian Dollar Trust (NYSEArca: FXA) is down over 3% the past month. The ETF is designed to track the movement of the Australian dollar versus the U.S. greenback.

The currency ETF has been a solid performer since the worst of the credit crunch passed in 2009, on a weaker U.S. dollar.

“The Australian dollar has strengthened significantly due to strong commodity exports to Asia as well as fiscal and monetary stimulus measures of the U.S. government,” says Morningstar analyst Michael Rawson.

Traders watch the Australian dollar as indicator for how comfortable global investors are with taking on risk. FXA also offers a decent yield of nearly 4%.