In this March 12, 2015, Don Brown of Hudson, a Fairpoint employee and member of the Communications Workers of America, speaks as dozens of labor activists meet at the State House in Augusta. Credit: Mario Moretto / BDN

The ranks of union workers in Maine, like elsewhere in the nation, have shrunk with the decades-long decline in manufacturing jobs, like papermaking. As this union presence continues to wane, some studies show it could be fueling the nation’s widening income gap.

Union membership as a share of the private sector workforce fell from 34 percent in 1979 to 11 percent in 2013, according to the Economic Policy Institute. Among men without a college degree, union membership fell over that same period from 38 percent to 10 percent. For women without a college degree, the decline was 16 percent to 6 percent.

In Maine, union representation — including the public and private sectors — has mirrored the national decline, falling from 14 percent of the state’s workforce in 2000 to 12 percent last year, according to data from the U.S. Bureau of Labor Statistics. The decline in unionization has been steepest in the private sector, while unions still maintain a strong presence in the public workforce.

That this decline is partly responsible for the growing wealth gap in the U.S. is the conclusion of a new report from the Economic Policy Institute, a left-leaning think tank founded with union support in 1981. Its authors looked at how the decline in union membership has contributed to the diminished economic power of private-sector workers not enrolled in a union.

Weekly wages for men unenrolled in a union would have been $52 higher in 2013 if the share of the workforce enrolled in a union had remained at its 1979 level. This translates to an extra $2,074 a year. For women not enrolled in a union, weekly wages would have been $13.80 higher, with an annual income boost of $745. The effect is less pronounced on nonunionized women because women weren’t part of union workforces as much as men in the 1970s.

The difference in weekly earnings is even greater for workers with less educational attainment.

For men without a four-year college degree not enrolled in a union, their weekly pay would have been $58 higher had the share of workers enrolled in a union remained at its 1979 level, with a yearly boost of $3,016. Nonunionized women without a college degree would have seen weekly earnings rise $12.59, with an annual increase of $679.86.

Men with a high school education or less would have seen weekly earnings $61 higher, or $3,172 annually, while women with the same education attainment would have seen weekly wages rise $13.39, or $723.06 annually.

Unions, the report’s authors argue, set a higher standard that boosts wages for all workers, by establishing pay and benefit standards that employers in nonunion workplaces eventually must adopt to reduce the incentive for their workers to unionize.

Maine also has seen a widening gulf in economic power between its lowest and highest earners. Since the 1970s, the top 20 percent of households saw their annual income rise 67 percent, while the bottom 20 percent of households saw a 27 percent increase, according to the Center on Budget and Policy Priorities, also a left-leaning think tank.

Other factors, though, also could account for the widening income gap. Improvements in technology have accounted for about 88 percent of manufacturing job losses between 2000 and 2010, according to a recent study by the Center for Business and Economic Research at Ball State University in Indiana.

Those jobs are historically the kind that have been unionized. Marc Cryer, director of the Bureau of Labor Education at the University of Maine in Orono, told the BDN last year that the loss of manufacturing jobs has been a strong factor fueling the decline in union membership.

Even as unionization declines in its traditional strongholds — manufacturing, construction, telecommunications — organized labor is growing in new sectors. A group of Maine lobstermen formed a union in 2013, and Shaw’s pharmacists voted to organize last year.

There is some evidence, too, that wage inequality is improving despite the decline in union membership.

The tightening labor market in Maine is fueling the fastest rise in the wage of the average Maine worker in more than a decade, according to Glenn Mills, chief economist at the Maine Department of Labor’s Center for Workforce Research and Information.