Union membership in the state remained unchanged at 12.6 percent in 2013, but a growing number of Ohio workers are represented by bargaining units, according to the U.S. Bureau of Labor Statistics.

The growth comes despite job losses in Ohio’s public sector, which has become a union stronghold, the data show.

The trend seems to be linked to manufacturers adding workers, some of which must be union jobs, because the industry has a fairly high rate of organized labor, said George Zeller, an economic research analyst in Cleveland.

“We are getting a slow recovery, and the main thing driving that is manufacturing,” he said. “Other industries are not as unionized as manufacturing.”

In 2013, about 605,000 workers in Ohio were members of unions, up 1,000 from 2012, while about 674,000 workers were represented by unions, an increase of 9,000, the data show.

The share of Ohio workers in unions remained the same in 2013, which mirrored the national trend. Union membership nationwide held steady at 11.3 percent.

But last year, the share of Ohio workers represented by unions increased for the first time since 2005, rising 0.2 percent to 14.1 percent.

About half of workers who belong to a union are employed in the public sector.

More than one-third of public sector workers are members of unions, while about one in 15 private-sector employees are union members, the government said.

But government employment in Ohio has been declining, falling 1.3 percent between December 2012 and December 2013.

Manufacturing employment, however, increased by 4,900 workers to 663,000 in the last year. About 11 percent of U.S. manufacturing workers are represented by unions.

“What growth we are getting has been concentrated in manufacturing,” Zeller said.

Few private-sector industries have a large share of unionized workers, but they include transportation and utilities (21.8 percent), educational services (15.1 percent), telecommunications (15 percent) and construction (14.9 percent), the bureau said.

But union membership in Ohio has plummeted by almost 30 percent in the last decade, and union representation has declined by nearly as much.

The number of people represented by unions has increased much more than union membership, which implies that more people may by opting out of joining the unions at their jobs, said Greg Lawson, a policy analyst for the Buckeye Institute, a conservative think tank.