occurred as a result of growth in the U.S. resident
population. Based on estimates from the U.S. Census Bureau, the number
of residents 18 and older increased from 145 million in 1974 to 210
million in 2001. Had the rates of first incarceration remained stable
at 1974 levels, the number of adults who had ever gone to prison would
have increased by an estimated 1.3 million.

In every year, the rates of first incarceration varied by age (figure
1). In 2001 sharply higher first incarceration rates were found for
each older birth cohort up to a peak of 350 per 100,000 at age 20.
These rates then dropped steadily with each older age category.

[Illustration: Figure 1: First incarceration rates]

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Figure 1

+First incarceration rates rose sharply among persons under age 45+

Number first incarcerated per 100,000 U.S. residents.*

Age at first
incarceration 1974 1986 1991 2001

12 0 0 0 0
13 0 0 1 0
14 1 0 6 0
15 6 8 27 12
16 25 29 67 58
17 66 81 139 152
18 107 143 219 254
19 142 203 295 325
20 140 217 307 350
21 143 209 306 344
22 133 188 274 329
23 132 172 285 304
24 113 164 261 285
25 92 153 254 280
26 81 142 227 274
27 79 128 224 282
28 79 116 210 262
29 68 116 189 268
30 55 112 179 244
31 45 107 164 243
32 40 93 148 217
33 38 87 123 206
34 36 82 120 196
35 38 78 125 198
36 36 74 126 195
37 34 68 114 177
38