Similarly, the generation life table for the 1970 birth cohort produced an estimated prevalence of 3.584% among those age 31 in 2001. Multiplying by 4,032,301 U.S. residents age 31 in 2001 resulted in an estimated 145,000 persons age 31 in 2001 who had ever been incarcerated. The estimated 5,618,000 adults ever incarcerated in 2001 was obtained by summing the number of persons ever incarcerated, age 18 or older. Dividing by the adult resident population of 210,207,901 yielded an estimated prevalence of ever having gone to prison of 2.673% in 2001. ---------------------------------------------------------------------- +Estimating prevalence of imprisonment in the United States+ To illustrate the application of generation life table techniques resulting in the 1.510% rate of ever having gone to prison among persons born in 1980, consider the following calculations: 1. Estimates of the number of persons in a population of 100,000 born in 1980 who died during each age interval were obtained by multiplying the age-specific mortality 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).