International Journal on Criminology Volume 1, Number 1, Fall 2013 | Page 37

International Journal on Criminology
"STOCK-FLOW" EQUATION: Consider an interval of time [t 0 ; t 1 ]. Let P 0 be the size
of the prison population at the initial date t 0 (period start), P 1 the size at date t 1 (period
end). Let E be the total number of entries into prison during the period and S the total
number of releases during the same period (except for transfers). The "stock-flow"
equation is expressed in the following relation: P 1 = P 0 +E−S, or P 1 − P 0 =E−S. Both
express the absolute increase during the period, or the balance.
INDICATOR OF THE AVERAGE TIME SPENT IN PRISON: This indicator can be
calculated by comparing the average number of people in prison for year n (P) to the flow
of entries into prison for the year (E): d = 12 × P/E or P = E × d/12 (d expressed in
months).
Strictly speaking, this formula corresponds to the demographic model of "stationary
population": the number of entries is constant from year to year, with the same release
schedule for all cohorts of entries. Of course, prison populations do not generally follow
this model. Also, this indicator hardly makes sense in economic terms, but it proves very
useful in determining basic trends (hence why I developed this expression in 1981).
EVENT: In the study of the penal system, we are not only interested in populations
involved in the criminal justice system, but also in the decisions that occur throughout the
criminal justice process (for example, indictment, committal, dismissal, conviction,
release) or other issues that impact these decisions (escape, suicide in prison, etc.). We
generally seek to identify the number of events, usually over a calendar year (flow), and
their relative frequency. The frequency is calculated by creating a ratio of the number of
events in a year to the population that is susceptible to experiencing that event (rate): rate
of entries to prison or detention per population size, and rates of mortality or suicide in
prison. We are also interested in the time lapsed between two events.
Among all these events, we make a distinction between those that are renewable, that
can happen again during the lifetime of a single person (e.g., new convictions for acts
committed after release), and those that are not renewable (e.g., death, conviction for the
first acts committed after release).
2. Two major variables: the nature of the offense and the penal category
In general demography, the most important variables are, for obvious reasons, sex and
age. Unsurprisingly, in the field of penal demography, the nature of the offense and the
penal category are central variables. These two variables are particularly complex to
analyze, both judicially and statistically. Sex and age also relate to the sociological
dimension of the penal field but at a secondary level, as do family situation, foreign
origin, nationality and origin, education, profession or work situation, health, addictive
behaviors, etc.
OFFENSE: In French law, criminal offenses are classified, according to their
seriousness, as felonies, misdemeanors, or petty offenses (art. 111-1 of the Penal Code).
Petty offenses are subdivided into five classes. With regard to felonies, the maximum
penalty—criminal imprisonment (ordinary offenses) or criminal detention (political or
military offenses)—is life imprisonment. For misdemeanors, the maximum penalty is 10
years imprisonment. Penalties for petty offenses include fines (a maximum of 1500 euros
for fifth-class offenses and in some cases, 3000 euros for repeat offenders) and the
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