the individual crime frequency indicates the number of criminal offenses an individual offender commits during a certain period, typically one year. In Anglo-Saxon literature, the annual individual crime frequency is often denominated by the Greek letter lambda.

Measurement of the annual individual crime frequency is a relatively recent development. Interest was sparked by a focus in American crime policy in the mid-1970s on the incapacitating effect of imprisonment. Confinement has an obvious preventive effect by physically inhibiting the confined from committing crimes. However, it was not until the first Philadelphia cohort study showed the uneven distribution of crime among offenders (Wolfgang, Figlio, and Sellin, 1972) that interest grew in using more goal-oriented confinement strategies (that is, to maximize the incapacitation effect).

To optimize this effect, it is necessary to predict individual crime frequencies, and this requires an understanding of the conditions responsible for variations in those frequencies. This was exactly the reason for the initiation of research in this area. The first study of individual crime frequencies is from 1978, a pilot study (Petersilia, Greenwood, and Lavin, 1978) for a subsequent (and better known) Rand Corporation study of self-reported criminality among inmates. One year later, Alfred Blumstein and Jacqueline Cohen published an article on individual crime frequencies which has achieved the status of pioneer work within the area of criminal careers research (Blumstein and Cohen, 1979).

Measuring Individual Crime Frequencies

Measurement of individual crime frequencies is based on offenders who are criminally active during a specific period in question.