The unionized share of the labor market went up a bit nationwide in 2007, and in Oregon and Washington, according to the most recent annual report by the U.S. Department of Labor’s Bureau of Labor Statistics (BLS).

Nationally, 12.1 percent of employed wage and salary workers were members of a union in 2007, compared to 12 percent in 2006. Since the work force grew in number, that meant 311,000 more workers were union members, bringing total U.S. union membership to 15.7 million.

According to an analysis by the Center for Economic and Policy Research (CEPR), a nonpartisan think tank, that one-tenth-of-a-percent increase is small, and may reflect statistical variation rather than an actual increase in the union membership share. Still, CEPR said, the uptick is striking because it is the first time since the BLS began collecting annual union membership rates in 1983 that the union share has increased.

In Oregon, union membership rose to 14.3 percent in 2007, from 13.8 percent in 2006, BLS reported. That meant 227,000 union members, 16,000 more than in 2006. And Washington union membership was the nation’s fourth highest, overtaking New Jersey, which was number four the previous year. Washington union membership was 20.2 percent in 2007, a slight increase from 19.8 percent in 2006. Total union membership in Washington rose 30,000 in 2007, to 579,000.

The estimates are based on the U.S. Census Bureau’s Current Population Survey, a nationwide monthly survey of a statistical sample of about 60,000 households. The union membership data comes from one-quarter of the sample and is reported as a percentage of wage and salary workers; unemployed and self-employed workers are excluded.

According to the BLS report, unionization was highest among public-sector workers, black men and older workers.

Public-sector workers had a union membership rate (35.9 percent) nearly five times that of private sector employees (7.5 percent). Within the public sector, local government workers had the highest union membership rate, 41.8 percent. And among occupational categories, education occupations had among the highest unionization of any, at 37.2 percent.

Within the private sector, the industries with the highest unionization rates were transportation and utilities (22.1 percent), telecommunications (19.7 percent), and construction (13.9 percent).

Notably, construction unions increased membership faster than the rate of job growth; the unionization rate was 13 percent in 2006.

Manufacturing, on the other hand, lost unionized jobs faster than the sector’s overall decline in employment. Union membership in manufacturing fell to 11.3 percent in 2007 from 11.7 percent in 2006. Manufacturing jobs were once identified with unionized employment, but today manufacturing workers are less likely to be in a union than the average U.S. worker.

Industries with the lowest unionization were agriculture (1.5 percent) and finance (2 percent).

Older workers were more likely to be union than younger workers — 16.1 percent of workers age 55 to 64 and 15.7 percent of workers 45 to 54 were union, while just 4.8 percent workers 16 to 24 were union.

Unionization was higher for men (13.0 percent) than for women (11.1 percent). But the gap has narrowed since 1983, when the rate for men was about 10 percentage points higher than the rate for women. Since then, unionization rates have declined for both men and women, but faster for men.

Blacks were more likely to be union members (14.3 percent) than whites (11.8 percent), Asians (10.9 percent), or Hispanics (9.8 percent). And within racial categories, black men had the highest union membership rate (15.8 percent) while Hispanic women had the lowest (9.6 percent).

And full-time workers were twice as likely as part-time workers to be union members (13.2 compared with 6.5 percent).

About 1.6 million workers were represented by a union, while not being union members themselves. Slightly more than half of them were employed in government.

Union members had median weekly earnings of $863 (which works out to $44,876 a year), while nonunion workers had median weekly earnings of $663 ($34,476 a year). Having a union to negotiate wages explains part of the difference, the BLS report explained, but there are other factors as well: union workers are more likely to be in higher-wage states, industries and occupations, and working for larger employers.

New York had the highest unionization rate (25.2 percent), followed by Alaska (23.8 percent), Hawaii (23.4 percent), and Washington (20.2 percent). Lowest in the nation was North Carolina (3.0 percent); next lowest were Virginia (3.7 percent), South Carolina (4.1 percent), Georgia (4.4 percent), and Texas (4.7 percent).

Just six states accounted for nearly half of the nation’s 15.7 million union members: California, with 2.5 million; New York, 2.1 million; Illinois, Michigan, and Pennsylvania, with 0.8 million; and New Jersey, with 0.7 million. Combined, the six states had 7.8 million union members.

For the first time, the unionization rate in the West (14.7 percent) exceeded the unionization rate in the Midwest (13.8 percent). California, which added over 200,000 union members in 2007, was where much of the growth took place. Illinois, conversely, weathered the largest loss of union membership of any state in 2007, as its share of unionized workers fell from 16.4 percent to 14.5 percent.

Union membership as a proportion of the workforce is still well below 20.1 percent, which was where it stood in 1983, the first year for which comparable data are available.

Oregon AFL-CIO President Tom Chamberlain admitted to some surprise at the union membership rise.

“Corporate America has been trying to drive a stake through our heart,” Chamberlain said. “But folks are figuring out how to organize even in the most difficult conditions.”

And in survey after survey, Chamberlain said, a majority of American workers say they want a union.