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 persons age 31 in 2001 who had ever gone to prison, the calculations were applied to the 1970 birth cohort. However, the rates of first incarceration (column 4) and mortality (column 2) used in the calculations were unique to the birth cohort. (Note the differences between Appendix tables 2 and 3.) ---------------------------------------------------------------------- <B>Appendix table 2. Estimating the prevalence of imprisonment in the U.S. population for persons born in 1980</B> Population of 100,000 births, 1980, reduced by mortality and incarceration in each successive year of age Number alive and not Rate of first Surviving incarcerated admission to Expected cumulative at beginning Number Expected State or number of number of Age at of age dying per number of Federal prison first first Prevalence first interval 100,000 deaths[a] per 100,000 admissions[b] admissions[c] percent[d] admission Year (1) (2) (3) (4) (5) (6) (7)