Paul Davidson

USA TODAY

Young low- and middle-wage workers are seeing their earnings rise more rapidly than their older, higher-paid counterparts, reversing the trend that prevailed early in the economic recovery.

The shift could boost economic growth since lower-paid workers tend to spend most of their paychecks, spreading the benefits throughout the economy. It's also lifting the fortunes of restaurant and retail employees whose stagnant wages have sparked protests across the USA.

In the third quarter, average hourly pay for workers earning less than $20,000 a year jumped 5.4% vs. the year-ago period, according to top payroll processor ADP. Those earning $20,000 to $50,000 got wage hikes of 4.9%.

Meanwhile, Americans making more than $50,000 a year received average raises of 4.3%.

"Workers who are not being paid very much are doing better," says economist Guy Berger of Royal Bank of Scotland.

ADP tracks the wages of 24 million employees of companies that contract with the firm to handle their payrolls. Its figures likely overestimate average U.S. wage growth because companies that can afford its services are doing better than U.S. businesses overall, says Mark Zandi, chief economist of Moody's Analytics which helps ADP compile its reports.

Yet the U.S. Bureau of Labor Statistics shows a similar trend. Workers at the 10th percentile of the pay ladder got average annual raises of 3% in the year ending Sept. 30, while earnings for the 90th percentile edged up 0.5%.

Low earners began to notch bigger pay increases about a year ago. By contrast, in the third quarter of 2012, wages for workers at the bottom rung fell slightly compared to the year-earlier period, while those at the top saw 2.6% growth, according to BLS.

Young workers, who tend to earn less, also have gotten sharply higher percentage increases in pay recently. Those ages 16 to 34 saw their paychecks grow about 6% the past year, ADP figures show, vs. 3.5% to 4.5% for older workers.

Economists aren't sure what's behind the recent acceleration in wage growth for lower-paid workers. Coming out of the recession, employers were stingy with the salaries of entry-level employees and may be making up for that with increases now that the economy is improving and the labor market is tightening, Zandi says.

Another factor is higher minimum wages in many states. And low-paying jobs in restaurants and bars have grown rapidly, forcing employers to compete for good workers with better pay.