Crime statistics inform public policy. For example, decisions about whether to spend money on prisons, crime prevention or victim services stem from cost-benefit analyses and costs of crime data. Proper allocation of funds for crime prevention, intervention, punishment, victim's services, and compensation requires an accurate characterization of crimes and their real costs to victims and society. Accurate measures of crime and costs contribute to assessing effectiveness of crime response programs. A paucity of data exists on criminal victimization of children and on the costs of such crimes.
Prevalence rates refer to numbers of people who have experienced crime.
But sometimes an individual is victimized repeatedly, as in the case of domestic violence and child abuse. Prevalence rates alone can underestimate crime occurrence and the severity of a crime's effect on and costs to an individual. Incidence rates are counts of victimization, and therefore more accurately reflect amount of crime. Ten rapes or beatings of a spouse are ten crime occurrences even though the victim is the same person. Earlier studies equated the number of victims with the number of crimes, underestimating the actual number of crimes and throwing off cost estimates accordingly.