Unions gained ground across the country last year, with membership accounting for 12.4 percent of the U.S. work force in the face of widespread job losses and a badly weakened economy.

In Colorado, the percentage of workers belonging to unions fell to 8 percent last year from 8.7 percent in 2007 as the number of jobs statewide increased by about 50,000 workers, according to data released Wednesday by the U.S. Bureau of Labor Statistics.

"The growth in the local work force last year is what accounts for that decline," said Ray Hogler, a Colorado State University professor specializing in labor issues. "There's still as much union representation as there was before. The change is almost statistically insignificant."

The Bureau of Labor Statistics reported that the percentage of workers represented by unions - including those not necessarily paying members of the unions - statewide stayed the same at 9.2 percent last year.

The total number of Coloradans belonging to unions edged down to 181,000 from 191,000 a year earlier, according to the government data.

Nationwide, the ranks of organized labor rose by 428,000 workers in 2008.

That's the biggest annual jump since the government began compiling the data in 1983. The increase marks the second year in a row that unions have added to their ranks.

Overall, union membership remains well below the peak of 35 percent during labor's heyday of the 1950s.

Membership was about 20 percent in 1983, the first year the bureau began compiling the numbers.

Unions have moved aggressively to bolster organizing efforts in recent years, a move that apparently offset the loss of 2.6 million jobs from payrolls in 2008. The Teamsters Union, one of the nation's largest unions, had its most successful organizing year in decades, with more than 43,000 workers joining.

Nationwide, public sector unions accounted for most of the increase last year.

The union membership rate for government workers rose to 36.8 percent from 35.9 percent in 2007.

In the private sector, membership remained steady as union ranks inched up to 7.6 percent from 7.5 percent in 2007.

The addition of about 89,900 workers to the Service Employees International Union's ranks accounted for another big chunk of the national growth.

Gary Chaison, a labor specialist at Clark University in Worcester, Mass., said the figures show the steady decline in union membership might have bottomed out.

"I think the unions are still vulnerable," Chaison said.

"It's almost as if they've settled down, but there really hasn't been any major growth spurt yet."

Keith Smith, a spokesman for the National Association of Manufacturers, said the numbers "reinforce to us that the system is working" and show that unions have exaggerated the need for labor law revision.

But union advocates note that only a fraction of new members last year came from newly formed unions, while the majority were already working in unionized workplaces.

Stewart Acuff, special assistant to AFL-CIO President John Sweeney, said the 428,000 new members last year is just a small portion of what unions could recruit if the card-check bill passes.

He cited union surveys showing nearly 60 million people would join a union "if there was no fear and intimidation."

The Associated Press contributed to this report.