In years past, rationing of electricity has sometimes resulted in reduced mining.

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The industry's shift to charging for fees for extra bags, or sometimes charging fees for any bags, has significantly reduced the rate of lost or mishandled bags.

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Sometimes organic versions of packaged foods are lower in sodium than regular and reduced-sodium versions, but not always.

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Visibility was reduced to the next street, or the next corner, or sometimes just the next step.

NPR: Elevating the World's Oldest Profession in Chicago

There have been many street demonstrations - sometimes violent - by Greeks angered by the job losses, pay cuts and reduced welfare resulting from the bailout deal.

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Studies generally show that a 1% increase in the marginal tax rate reduced taxable income by 0.1-0.4%, though sometimes and in some places it may be higher.

ECONOMIST: Taxing the wealthy

"Furthermore, unintended consequences are sometimes difficult to quantify, " Goldberg says, citing higher costs to consumers and businesses, reduced availability of credit, lager banks being placed at a relative disadvantage to smaller ones and so forth.

FORBES: Regulatory Reform