Robert H. Perry's  2022 Contract Security Industry White Paper

Security Advisor Newsetter Winter 2022

Security Letter:  2021 List of Largest Guard Companies in the U.S. 

Security Advisor Newsletter Summer 2021

U.S. Department of Labor/Bureau of Labor Statistics:

2021 Employment and Wage Data for Security Guards

2021 Occupational Outlook Handbook - Security Guards

Security Letter:  2020 List of Largest Guard Companies in U.S. 

Security Letter:  2019 List of Largest Guard Companies in U.S.