The Sunlight Foundation has done an impressively detailed data analysis of the lobbying on immigration since the last big reform effort in 2007, combing through 6,712 quarterly reports from 678 registered lobbying groups. Researchers tracked the bills mentioned in the disclosures to determine the specific issues that these lobbyists focused on and how active they were in pushing Congress on them.
In total, these groups spent more than $1.5 billion on immigration lobbying between 2008 and 2012—and that was almost all before the newest comprehensive reform effort heated up, Sunlight notes. Here's their list of the kinds of groups that have been most actively pressing Congress on the issue, based on how concentrated their lobbying has been.
The Sunlight Foundation also mapped out the immigration lobbying landscape, with the circles indicating a high concentration of activity by lobbying groups: