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Thousands of airport security screeners could choose a union to represent them as early as March, marking the latest expansion of union influence in the public sector, which now has more labor union members than the private sector.

Though union membership nationwide is declining, data released Friday by the Bureau of Labor Statistics show that of the 14.7 million workers who were members of a union in 2010, 7.6 million work in government jobs while 7.1 million are in the private sector.

The overall labor union membership fell from 12.3 percent to 11.9 percent of the working population. But with fewer workers under government than in businesses, the membership rate reached 36.2 percent for public sector employees, compared with just 6.9 percent for the private sector.

Participation was highest for local government workers, whose generous retirement and other benefits have contributed to long-term budget deficits in states across the country.

But employees for the Transportation Security Administration could make the federal unionized labor force much stronger. After a meeting among representatives from TSA, the Federal Labor Relations Authority and the two unions vying for TSA's employees, a tentative vote was scheduled for March 9 to decide whether to organize, and if so, with which union.

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The election, covering more than 40,000 employees, will be the largest in federal government history, according to the National Treasury Employees Union, which is competing with the American Federation of Government Employees during the six-week balloting process.

Both unions are pressing for collective-bargaining rights in the very-near future, a possibility that has troubled lawmakers in the past.

"Employees should have had (collective-bargaining rights) from day one," NTEU President Colleen Kelley told FoxNews.com, expressing concern that TSA workers are worried about "favoritism" at the agency -- something she claims her union could address.

"If those workplace rules are rules employees don't see as fair ... then you're going to have a work environment that is not a healthy one for employees and not a healthy one for the agency. And that's what currently exists at the TSA," she said.

Others aren't so sure whether a unionized TSA workforce is a positive step.

"Unionization typically means two things: higher costs for employment and no change in productivity; in fact, maybe even a backsliding in productivity," said Daniel Griswold, director of the Cato Institute's Center for Trade Policy Studies. "Bottom line is we're going to get less security for the dollar, or pay more for the same amount of security."

Sen. Jim DeMint, R-S.C., has also expressed security concerns regarding the possibility of collective-bargaining rights at the TSA. Asked for comment on the upcoming TSA vote, DeMint's office referred FoxNews.com to prior statements in which DeMint described the unionization of TSA as a "homeland security disaster."

DeMint said TSA workers need to be "responsive and adaptive to terrorist threats," suggesting that ability might be hampered by a stronger union presence. He expressed concern that the move would add new layers of bureaucracy to an agency that values quick response.

He also warned that collective bargaining would compel TSA managers to share intelligence with the union and that TSA managers would face a tougher time rewarding good workers and firing bad ones.

But Cathie McQuiston, AFGE's deputy director of its membership and organization department, said TSA's management would retain the flexibility to respond in an emergency just like any other department. "There's no exemption for TSA, they'd be covered the same."

She also noted that union activity like striking is prohibited in the federal sector, meaning Washington need not worry about droves of TSA screeners picketing airports. Her union already represents some TSA workers at the local level.

According to BLS figures, union members enjoy measurably higher pay than their non-union colleagues, another source of consternation for budget hawks who say the government is paying its employees too much. The report showed union members overall had median weekly earnings of $917, compared with $717 for non-union workers.

Griswold, though, said the tide may be turning for public-sector unions. He said taxpayers are "connecting the dots" between union work forces and "exploding" budget deficits, leading to less public sympathy for the importance of union-negotiated benefits.

"It's catching up to them eventually," he said.