The Difference Between Reported and Estimated Fire Data

What is the difference between reported fire incident data and estimated fire incident data, and why is the difference important? This NFIRSGram explains how national fire estimates are calculated using reported incident data and National Fire Protection Association estimates.

As of 2015, there were nearly 30,000 fire departments in the United States. Of that number, only about 74 percent of fire departments reported their fire incident data to the National Fire Incident Reporting System (NFIRS).

What is an estimate?

In simple terms, the practice of estimating means using something that we know about a portion of a population to approximate something that we do not know about the whole population. In this instance, we use the reported fire data in NFIRS (something that we know about 74 percent of fire departments) and data from the National Fire Protection Association’s (NFPA’s) annual Survey of Fire Departments for U.S. Fire Experience to estimate the total number of fires within a specific category in the U.S. (something that we do not know).

Why do only 74 percent of fire departments report data to the National Fire Incident Reporting System?

NFIRS was created as a result of the National Fire Prevention and Control Act of 1974 (P.L. 93-498) which mandated collecting national data on fires. The law also directed the USFA to encourage and assist state, local and other agencies — public and private — in developing and reporting information; however, there is no specific requirement to report. Because NFIRS is a voluntary system, not all states or fire departments within states participate.

How does the U.S. Fire Administration create a national-level estimate of fires for the United States?

Because NFIRS data are not based on a statistically selected sample and do not represent the total number of fire incidents, the raw reported NFIRS data must be scaled up to create national estimates. These estimates are based on a method of apportioning the NFPA estimates for total fires, structure, vehicle, outside, and other fires. Generally speaking, the national estimates are derived by computing a percentage of fires, deaths, injuries or dollar loss in a particular NFIRS category, and multiplying it by the corresponding total estimate from the NFPA annual survey.

How are the different data (raw reported National Fire Incident Reporting System data and national fire estimates) used by different organizations?

NFIRS data are used at all levels of government. At the local level, a department’s reported incident and casualty information may be used for setting priorities and targeting resources. The data now being collected are particularly useful for designing fire prevention and educational programs and Emergency Medical Services-related activities specifically suited to the real emergency problems the local community faces.

On the state level, reported NFIRS data may be used in many capacities. One valuable contribution is that NFIRS data are used by state legislatures to justify budgets and to pass important bills on fire-related issues, such as sprinklers, fireworks and arson.

Many federal agencies, in addition to USFA, make use of both detailed reported NFIRS data to examine specific fire problems and national-level estimates. Some of these agencies are the Consumer Product Safety Commission (CPSC), the National Highway Traffic Safety Administration, and the National Institute of Standards and Technology. The CPSC has found NFIRS very useful in identifying potentially hazardous products.

National-level estimates may also be used by various private industries, including national associations for home appliance product manufacturers, the hotel and motel industry, insurance companies, and attorneys to determine the overall scope of the fire problem.