All Employees: Professional and Business Services: Investigation and Security Services in Illinois was 39.47419 Thous. of Persons in January of 2024, according to the United States Federal Reserve. Historically, All Employees: Professional and Business Services: Investigation and Security Services in Illinois reached a record high of 39.81016 in September of 2017 and a record low of 24.30903 in April of 1991. Trading Economics provides the current actual value, an historical data chart and related indicators for All Employees: Professional and Business Services: Investigation and Security Services in Illinois - last updated from the United States Federal Reserve on April of 2024.