They are designed to double or triple the performance (or the inverse of the performance) of the target index when held for a day.

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The UltraShort Financials ProShares moves at a rate double the inverse of the Dow Jones U.S. Financials index.

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This ETF seeks daily investment results, before fees and expenses, that correspond to the inverse of the daily performance of the FTSE China 25 Index.

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Dozens of "inverse" ETFs move in the opposite direction of their underlying index or basket of securities.

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Inverse options for the midcap group include the ProShares UltraShort Midcap 400 Index Fund ETF (MZZ).

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However, the inverse trading relationship between gold and the U.S. dollar index has become less pronounced that it had been in recent months.

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