There's money in mopping.

Dateline: AUSTIN

UNIONS have never had much luck in the South. The region is home to Wal-Mart and other arch-foes of organised labour. For years, car plants have been built in Tennessee or Alabama to escape the grip of Detroit. So last week's announcement that nearly 5,000 janitors (cleaners and caretakers) in Houston were joining the Service Employees International Union (SEIU) was a rare breakthrough. Julius Getman, a professor at the University of Texas, thinks it is the largest union victory in the South in decades.

The SEIU takes a different approach to organising. It has organised janitors at several big companies at once. Rather than mounting a campaign at each workplace separately, it will negotiate one big industry-wide contract. This, in theory, eliminates each cleaning company's fear of being undercut by competitors if it allows higher wages. The companies agreed to stay neutral. The strategy bypasses the National Labour Relations Board, which usually oversees the unionisation of workers. That is a bonus in a place like Houston, where undocumented workers would rather not get the government involved.

Janitorial success has come to be quite a hallmark of the SEIU which, with 1.8m members, is one of the largest unions in the country. The "Justice for Janitors" campaign has been going for 20 years. The SEIU claims triumphs from Los Angeles (raising pay by more than 25%) to Chicago (getting employer-paid health benefits). Pay talks will start soon in Houston, and the SEIU will be under pressure to deliver. The starting point could hardly be lower. According to the union, Houston's janitors earn an average of $5.30 an hour, less than half what their counterparts in Philadelphia get.

Whether the Houston milestone will lead to other triumphs in the South is an open question. Nonetheless, it is a small boost for a movement that has been going through tough times recently. Union membership is in steep decline in the private sector. This summer the SEIU and a few other unions split from the AFL-CIO, America's big labour federation. Since then, the SEIU has been pursuing new strategies to boost its membership.