Security Advisor Newsletter Winter 2021 (Security Magazine)
Robert H. Perry's 2020 Industry Review and 2021 Outlook
Robert H. Perry's 2020 "White Paper" on the State of the Contract Security Industry
Security Letter: 2020 List of Largest Guard Companies in U.S.
U.S. Department of Labor/Bureau of Labor Statistics:
2019 Employment and Wage Data for Security Guards
2019 Occupational Outlook Handbook - Security Guards
2018 Security Magazine List of Top Guarding Companies