US personal incomes jumped 2.6 per cent in December, the biggest monthly increase since 2004, as high earners sought to beat a New Year tax rise.The month was marked by accelerated bonus and dividend payments, the US Commerce Department said.Income tax cuts dating back to George W. Bush’s presidency were due to expire in the New Year as part of the ‘fiscal cliff’ of tax rises and spending cuts.Despite the boost to incomes, consumer spending rose only 0.2 per cent in the month."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.In the event, the tax rises went ahead only for individuals earning more than $400,000 as part of a last-minute deal negotiated between Republicans and Democrats in Congress to avert the fiscal cliff, with the top tax rate rising from 35 per cent to just under 40 per cent.