There is no absolute source of the numbers of fires in the United States each year.
Many fires are small and go unreported.
Some fires are reported but if there is no monetary loss they are not tabulated. Half the nation's fire departments participate and collect data on nearly a million fires each year. The lack of data, especially for fatal fires, masks the true picture of the fire problem. In making national estimates, the unknowns should not be ignored. The approach taken in putting together this information was to distribute the fires for which the cause is unknown in the same proportion as the fires for which the cause is known, which may or may not be approximately right.