Labor unions in the United States have been losing members for years. Not all are shrinking, however. The nation's fastest-growing union has recently added thousands of members in Houston, Texas. The expansion is the result of an effort to organize the workers who clean buildings.

The Service Employees International Union has close to two million members. It organizes workers in a number of service areas. These include health workers, government and public service workers and workers in property services.

In Houston, janitors at four major companies have voted to unionize. The American Arbitration Association recognized the decision as official on November twenty-ninth. Four thousand seven hundred janitors in Houston have now joined the Service Employees International. 

That number is more than sixty percent of the janitors in large buildings in the city. It could increase to over seventy percent if workers at another company are able to unionize.

The Houston janitors say they want the union to help them negotiate better pay. They also hope for some form of health plan and retirement savings. 

Currently, the janitors receive about five dollars and thirty cents an hour. That is a little above the national minimum wage of five dollars and fifteen cents. The minimum wage is the lowest pay that workers can receive. 

Unionized janitors in cities like Chicago, New York or Washington, D.C., earn eleven dollars or more. But most cleaning workers around the country do not belong to unions. Many workers in low-paying service jobs are recent immigrants. Some are in the country illegally. 

The Houston area is not known for organized labor activity. The union did not even have offices there. Organizers from Chicago supervised the effort.

In July, the Service Employees International Union split with the A.F.L.-C.I.O. That came as part of a major division within the country's main labor alliance. 

Andrew Stern is president of the service employees union. He says twenty-first century unions must organize by industry across borders, to deal with huge international companies. 

Fifty years ago, about thirty-three percent of privately employed workers in America were in a union. By the early nineteen eighties it was twenty percent. Today about thirteen percent of American workers belong to unions.