Union members represented 11.3 percent of the American workforce in 2012, a drop from 2011’s 11.8 percent, according to the Bureau of Labor Statistics.

Labor unions have declined in size for years as the trade and manufacturing industries that supported union jobs have receded.

The public sector, which has the highest rate of unionization in the country at nearly 36 percent of the workforce, was not able to avoid the impact of the fiscal crisis. States, overburdened by rising costs and smaller tax revenue, are beginning to lay off government employees.

The loss of jobs in labor-friendly sectors has been coupled with the retirement of aging members. Compounding the problem for labor unions is the fact that young people are joining unions at a lower rate than previous generations. Nearly 15 percent of workers aged 55 to 64 belong to labor unions, more than triple the rate of workers aged 16 to 24.

The rise of right-to-work laws, which prohibit forced unionism, in traditional labor strongholds in the Midwest could speed the decline of labor unions, experts say.

Indiana became the first right-to-work state in the region in February 2012. Membership rates plummeted: About nine percent of state workers belonged to unions in 2012, down from 11.3 percent in 2011.

Michigan, which has more than 600,000 union members, will officially become a right-to-work state in March after passing similar legislation in December.

Pennsylvania Republicans on Tuesday introduced legislation to make it the 25th right-to-work state in the country and the first in the Northeast. Pennsylvania has 700,000 union workers.