According to some statistics, 500, 000 to 5 million elders are abused, exploited or neglected each year in the US. These numbers vary widely since elder abuse is sometimes hard to fine and frequently is hidden.

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The mandates vary by state, too, making it hard to grow.

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Preparations of the herb, including the amount of valerenic acid, vary widely from study to study, making it hard to draw firm conclusions, says Catherine Ulbricht, co-founder of Natural Standard and a pharmacist at Massachusetts General Hospital in Boston.

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How hard a speeding ticket hits you in the wallet can vary according to several factors, including how fast over the limit you were going, no matter where in the country you're caught.

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Forecasters have said changing wind patterns made it hard to predict the cloud's exact path and concentrations would vary between regions.

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That makes it hard to introduce uniform pricing of derivatives, because the penalties (or lack of them) for defaulting vary so much from one jurisdiction to another.

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