From the Executive Summary: "The 2016 'Arson Incident Report (AIR)' is an informational product prepared by the United States Bomb Data Center (USBDC), using incident data reported in the Bomb Arson Tracking System (BATS) by its nearly 2,500 interagency partners and 12,153 registered users. This report examines the total number of fire-related incidents reported in BATS for calendar year 2016 and includes 'Incendiary (Arson), Undetermined, Accidental' and 'Natural' fire-related incidents. It is important to note that BATS is a real-time dynamic incident management system that is strictly user dependent; therefore, it is possible that the data represented in this report may differ slightly from previously reported data due to updates or changes made by the owner of individual records. The reader should also be aware that when compared to the data reflected in the Uniform Crime Report and/or National Fire Incident Reporting System, the number of incidents reflected in BATS captures approximately 20 percent of the annual incendiary (arson) fires reported. Due to this limited dataset, the USBDC cautions the use of this report for analytical purposes."
Bureau of Alcohol, Tobacco, Firearms and Explosives: https://www.atf.gov/