Union membership in the United States is down slightly, accounting for just over 11 percent of the workforce last year, the Labor Department reported Friday.

That's just a fractional drop from the year before.

The department's Bureau of Labor Statistics said public-sector workers have the highest union membership rate at nearly 36 percent. That's more than five times higher than membership of private-sector workers at less than 7 percent.

Workers in education, training and library jobs and in protective service jobs have the highest unionization rate, at 35 percent.

Earnings were higher for union members last year, at $970 a week versus $763 a week for non-union members.

With 58 months of consecutive job growth, the report shows that "workers made great strides and confronted great challenges" during 2014.

AFL-CIO President Richard Trumka cited "major organizing wins" last year, including one at American Airlines.  Trumka also cited "multiple state victories on (raising) the minimum wage and innovative campaigns conducted by carwash workers, among others."

Labor Secretary Thomas E. Perez said the report demonstrates that "the economy is resurgent, with an unemployment rate well below 6 percent and job growth we haven't experienced since the late 1990s."

"When unions are strong, working families thrive, with wages and productivity rising in tandem. But when the percentage of people represented by unions is low, there is downward pressure on wages and the middle class takes it on the chin," Perez said.

The percent of workers who were members of unions in 2014 was 11.1 percent, down from 11.3 percent each in the two preceding years.

One of the sharpest year-to-year drops in union membership came in Michigan: from 16.3 percent in 2013 to 14.5 percent in 2014. The decrease came in the first full year under the state's right-to-work law.

Among states, New York continued to have the highest union membership rate, at 24.6 percent while North Carolina once again had the lowest rate at 1.9 percent.

In raw numbers, 7.2 million employees in the public sector belonged to a union in 2014, compared with 7.4 million workers in the private sector.

Within the public sector, the union membership rate was highest for local government at 41.9 percent of the workforce, "which includes employees in heavily unionized occupations, such as teachers, police officers and firefighters," the report said.

Black workers had a higher union membership rate in 2014 (13.2 percent) than workers who were white (10.8 percent), Asian (10.4 percent) or Hispanic (9.2 percent).

North Carolina's 1.9 percent membership rate was followed by South Carolina, 2.2 percent, and Mississippi and Utah, each with a 3.7 percent rate.

New York had the highest unionization rate at 24.6 percent, followed by Alaska (22.8 percent) and Hawaii (21.8 percent)