Exact death and injury counts are not possible; especially for large events and events before 1955.
Prior to 1950 in the United States, only significant tornadoes are listed for the number of tornadoes in outbreaks.
Due to increasing detection, particularly in the U.S., numbers of counted tornadoes have increased markedly in recent decades although the number of actual tornadoes and counted significant tornadoes has not. In older events, the number of tornadoes officially counted is likely underestimated.
Grazulis, Thomas P. (1993). Significant Tornadoes 1680-1991, A Chronology and Analysis of Events. St. Johnsbury, VT: The Tornado Project of Environmental Films. ISBN1-879362-03-1
