The Denominator Blindness Effect: Accident Frequencies and the Misjudgment of Recklessness

People seriously misjudge accident risks because they routinelyneglect relevant information about exposure. Such risk judgmentsaffect both personal and public policy decisions (e.g., choiceof a transport mode) but also play a vital role in legal determinations,such as assessments of recklessness. Experimental evidence fora sample of 422 jury-eligible adults indicates that people incorporateinformation on the number of accidents, which is the numeratorof the risk frequency calculation. However, they appear blindto information on exposure, such as the scale of a firm's operations,which is the risk frequency denominator. Hence, the actual observedaccident frequency of accidents/exposure is not influential.