"We do think it is clearly negative for holders of commercial debt, that is our view, that it will weigh on countries' capacity to serve their commercial debt, " he said.

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Facebook told the developers the decision had been made following negative feedback from account holders.

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Today, yields aren't as deeply negative, but bond holders are still losing money compared to inflation.

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House prices have halved since the Ireland's property market peaked in 2007, leaving an estimated 400, 000 mortgage holders with negative equity.

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Although that performance was much better than the painfully negative returns suffered by holders of government bonds, it was a long way short of the 6-7% returns that shares have historically achieved.

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"The negative crowd psychology serves to clear out weak holders from the market and prepares the way for the next advance, " says Spear, who is looking for the Dow to hit 9, 400 to 9, 600 by late December.

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However, delinquency is substantially more common among those more deeply underwater than those in less negative equity: only 5.5% of mortgage holders between 0 and 20 percent underwater are delinquent on payments, as compared to 16% of mortgage holders who are greater than 100 percent underwater (see Figure 3).

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The smaller float creates bigger gains in rallies when buying pressure dominates and there are fewer stock-holders willing to sell, but larger declines if unexpected negative news brings in selling pressure, since there are fewer bargain hunters aware of the stock and looking to buy.

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Faced with negative real interest rates, rapidly rising inflation, and a chronically weak dollar, foreign holders of US Treasury debt and other dollar-denominated holdings may begin to lose their nerve.

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