Amid plunging gold and oil prices, some market observers are saying the commodities boom has met its end. Recent disappointments by Australian equities and the corresponding U.S.-listed exchange traded funds seem to be affirming as much.

Last month, Australian stocks were the second-worst offenders among developed markets tracked by S&P Dow Jones Indices. The only developed market that performed worse was Norway, which was home to an almost 9.1% equity market decline. As one of the largest non-OPEC, developed markets producers of oil in the world and heavily dependent on crude to drive government revenue, weakness in Norwegian shares as oil falters is not surprising. [Oil Saps These International ETFs]

Although Australia is not a major oil exporter, the iShares MSCI Australia ETF (NYSEArca: EWA) has plunged more than 18% since peaking in early September. Making EWA’s decline all the more ominous is that the Reserve Bank of Australia has been successful in weakening the Australian dollar. The CurrencyShares Australian Dollar Trust (NYSEArca: FXA) is off 10.5% since early September. [Remember These Forex ETFs]

Slumping commodities prices and the inability of EWA to react favorably to the weaker Aussie threaten the ETF’s tendency for notching strong December showings. Since 2000, EWA, the largest Australia ETF, has risen 10 of 13 times in the final month of the year, according to PastStat data.

Of ETFs tracking stocks in G-20 nations with at least 13 years of trading history, EWA’s 77% December win rate is topped only by the iShares MSCI Brazil Capped ETF (NYSEArca: EWZ). EWZ, the largest Brazil ETF, has risen in 12 of the past 13 Decembers. [A Santa Claus Rally for Brazil ETFs]

EWA posted an average September gain of 3.1% over the past 13 years, according to PastStat, but this year could be different although investors have poured nearly $30 million into the ETF this quarter.