This double taxation is one reason the U.S. has long had a differential tax rate for capital gains.

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Another negative factor for the U.S. dollar remains the interest rate differential outlook or the official monetary policy rate.

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And to top it all off, that rate differential seems to be blowing out.

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If they raise interest rates, they increase the interest rate differential which makes owning the currency more attractive.

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In recent years the U.S. has improved relative to Japan in terms of productivity and the terms of trade, and the interest-rate differential has widened in America's favor.

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Because they make their money on the interest rate differential.

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With the U.S. Federal Reserve calling for near zero interest rates through mid 2013, that leaves the U.S. dollar on the bearish side of an interest rate differential play.

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In the late 1990s, the black-white wage differential closed at the fastest rate since the civil rights era.

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His strategy is unusual among cancer researchers, who have tended to focus on identifying cancer-causing genes rather than writing differential equations to describe the rate of tumor spread.

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By reducing the discount rate, the Fed intentionally abandoned the traditional one percent differential in order to deal with the crisis.

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