rate (Appendix table 2, column 2) by the
number of persons alive and not previously incarcerated at each age
(column 1).

* For example, among persons who reached age 21 without having been
previously incarcerated, a total of 92 were estimated to have died
(column 3) before reaching age 22 (that is, 96,607 times the mortality
rate of 0.000955).

2. The number of persons in the 1980 cohort who were at risk to
incarceration during an age interval was then calculated by subtracting
the number dying from the number of persons who were alive and not
previously incarcerated at the beginning of the age interval (column 1
minus column 3).

* An estimated 96,515 of the persons who survived to age 21 without
being incarcerated were at risk to first incarceration at age 21.

3. The number of persons in the original 100,000 population estimated
to have been admitted to prison at each age (column 5) was then
obtained by multiplying the age-specific first admission rates (column
4)by the number of persons alive and not previously incarcerated.

* Among persons born in 1980 who had not been previously incarcerated
by age 21, 343 were estimated to have been incarcerated before they
reached age 22 (that is, 96,515 times the first incarceration rate of
.003557).

4. The number of living persons at each age who had ever gone to
prison was then calculated by summing the number going to prison for
the first time during that year of age (column 5) plus the number of
members of the 1980 birth cohort who previously went to prison and
survived until the next year of age (column 6 times the survival rate,
not shown).

* Of the 1,132 persons who had gone to prison and reached age 20,
1,131 survived to reach age 21. An additional 343 persons were expected
to be incarcerated for the first time before reaching age 22 (for a
cumulative total of 1,474).

5. The percent of persons at each specific age who had ever gone to
prison (column 7) was then calculated by dividing the number of persons
who had ever gone to prison and were still alive (column 6) by all
persons who were still alive (including persons never incarcerated plus
ever incarcerated).

* Among persons age 21, the prevalence rate was 1.510%, obtained by
dividing 1,474 (column 6) by 97,646 (column 1 minus columns 3 and 5,
plus 1,474), times 100%.

Prevalence rates for other birth cohorts were calculated using similar
procedures. For example, to estimate the percent of