For investors of the best performer among 2,600 U.S. funds tracked by Bloomberg, not even a 46 percent return this year is enough to persuade them to hang tight. Market Vectors Gold Miners ETF, tops among funds with at least $1 billion in assets, saw a fourth straight quarterly outflow as price swings in mining shares proved more than some people could stomach, according to Sameer Samana, a St. Louis-based global quantitative strategist at Wells Fargo Investment Institute. A gauge of volatility in the NYSE Arca Gold Miners Index tracked by the ETF has been twice as high as bullion, prompting investors to move their money into gold and away from the companies that produce the metal, Samana said.

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