NEW YORK - Markets around the world are on the edge of their seats awaiting a key US jobs report later on Friday (Sept 4) that is seen as key to the timing of the first Federal Reserve interest rate hike in nearly a decade.

The bet is that should the report show that more than 220,000 jobs were created in August, then the US central bank is likely to vote to raise interest rates at its next meeting on Sept 16-17.

But that number, nor the expected fall in the jobless rate to 5.2 per cent, does not tell the whole story of employment in the US.

Despite the new jobs being created, workers' real wages, including the cost of living, are going backward.

CNBC reported on Thursday that average pay in real terms slumped 4 per cent from 2009-14, according to the National Employment Labor Project.

What's more, the kind of jobs that have been most plentiful during the post-Great Recession boom have seen some of the biggest declines in pay, said CNBC.

Restaurant workers, whose ranks have swelled by 376,000 over the past year, saw real pay declines of 8.9 per cent for cooks, 7.7 per cent for food prepares and 4.8 per cent for waiters and waitresses.

"Our findings on occupational wage declines are consistent with a longer-run trend in wage stagnation and growing income inequality for America's workers," NELP was quoted as saying.

"Reversing these trends will require concerted effort on the part of federal, state, and local policymakers, regulators and private-sector leaders to reorient our economy toward better-paying jobs," it told CNBC.