The Bank has said that it was waiting to see the effect of bonus payments on wages before making a decision to raise interest rates further.

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Existing U.S. law defines earned income as salary and wages, commission, bonus, professional fees and tips received for personal services.

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"Personal income in November and December was boosted by accelerated and special dividend payments to persons and by accelerated bonus payments and other irregular pay in private wages and salaries in anticipation of changes in individual income tax rates, " the Commerce Department's Bureau of Economic Analysis said.

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The bonus, though, doesn't make up for the higher wages that adults command.

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