(Undated) -- Immigrants from Mexico often fill the gap where there's a need for agricultural or low-skilled work in the U-S. But a new study finds there is little benefit for those who legally obtain a temporary worker visa. Researcher Lauren Apgar found that temporary workers hold jobs with the lowest occupational standing, and with wages equivalent to those of undocumented workers. And their visa requires that they work for the sponsoring employer, which she says prevents advancement. Apgar says one solution would be to reform the temporary workers' program so that visas are issued directly to workers, instead of employers. She says this would make the program more attractive to currently undocumented immigrants.