There remains substantial uncertainty about whether this drug is worth taking.

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This forecast is of course subject to substantial uncertainty.

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In every direction there is uncertainty, fear, trepidation, and yes, a substantial perception of risk.

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At the time, there was considerable uncertainty among demographers and actuaries about whether or not the substantial increase in life expectancy seen in the past couple of decades would continue or start to tail off.

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So uncertainty remains for a market that has probably already factored in a substantial new round of stimulus.

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