prevalence refers to the proportion of the population that commits crime during a given year. In the English-language literature the term “participation” is used synonymously with “prevalence.”

Prevalence studies often begin with comparisons of prevalence across age and gender. Yet, in spite of general agreement about the method for prevalence measurement, great difficulties arise in comparing results from different studies. Prevalence rates are calculated by dividing the number of criminally active offenders by the total number of inhabitants. In this fraction, the value of the denominator – the population unit – causes few problems. However, the numerator – the criminally active part of the population – is fraught with measurement error since study methods, boundaries, and definitions can vary considerably. This makes it almost impossible to compare results across studies, especially those between different countries.

The magnitude of the prevalence rate depends first and foremost on whether the information defining the “criminally active” stems from studies of self-reported criminality or from studies of registered crime. Self-report studies will generate prevalence rates several times greater than those of registered crime.

Cross-national differences will remain within both self-report and register-based studies and will affect the results. This is due to differences in how crime is defined. What does it mean to be “criminally active”? Does it include all types of offenses or only violations of the penal code? In register-based studies,“crime” can be defined quite differently across jurisdictions. Clearly, the more broadly “crime” is defined, the greater the apparent prevalence will be.