(Bloomberg) -- ETF investors are missing the silver party.

Instead of piling into the asset that's offered the biggest gain among 22 raw materials on the Bloomberg Commodity Index this year, ETF investors are retreating. iShares Silver Trust, the biggest ETF backed by the metal, is poised for a fifth straight monthly outflow, a trend not seen since the fund listed in 2006. Holdings in all silver-backed ETFs tracked by Bloomberg have shrunk by 6.2 million ounces and are near the lowest in seven months.

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