A study released Aug. 16 by the Center for Urban Economic Development at the University of Illinois at Chicago and Warehouse Workers for Justice found that 81 percent of new hires and 63 percent of all workers in warehouses were temporary employees; they earned a median $9 an hour while direct-hires earned $12. One in five warehouse workers have been hurt on the job, it found, and a third of them did not report their injury for fear of being punished or fired. A third of those who did report an injury said they suffered retaliation.

The study was based on 319 interviews conducted by warehouse workers, an example of the “participatory research” model wherein those affected by a given issue collect information that is then analyzed by academics. Mr. Mwaura said the report was a jumping-off point for more in-depth studies zeroing in on various aspects of the industry.

A 2006 study by the Centers for Economic Development in Will and Grundy Counties found that a majority of warehouses used temporary agencies to hire employees, and that 10 percent were temporary workers on a permanent basis. That study reported an average wage of $11 to $24 an hour depending on the job.

John Greuling, president of the Will County Center for Economic Development, said civic leaders were proud to be a national hub of the logistics industry. When farms were converted to warehouse sites, Mr. Greuling said, the amount of property tax dollars available to schools skyrocketed. The thousands of unskilled jobs in the warehouse business go to workers who might have few other options, he said.

But Mr. Greuling said local officials were also concerned about complaints of truck traffic, air pollution and the preponderance of low-wage temporary positions.

“We know there are probably too many entry-level jobs, there are folks who work in these centers but don’t earn enough to live in Will County,” he said. “Does everyone want to stay at $12 an hour forever? I imagine not. Do temporary agencies take advantage of immigrants here without papers? I imagine they do. These are challenges larger than our local problems.”