A tough job market has reduced the population of undocumented immigrants in Arizona by one-third over the past two years, according to a report issued by the Center for Immigration Studies, a Washington, D.C.-based organization. The study also suggested that more illegal workers are returning to their homelands. In a story about the report, the Arizona Republic’s Daniel Gonzalez points out the organization favors less immigration. He also points out some of the economic effects the decline is having on the Arizona economy, including the recent closure of number of a number of groceries in predominantly Latino neighborhoods