Note that the data are normalized so that both reported crime events and inmates in state and federal detention are expressed as ratios — per 100,000 population. This brings home the fact that our property and our persons are significantly less safe today than they were four decades ago — and that a larger percentage of the population lives behind bars.
Note next that the data are charted on a logarithmic scale. This means that the growth and/or decline rates of values — the slope of the curves — can be compared without scale distortions. Note next that the crime rate — both property and violent crime, increased at a brisk rate to about the mid 1970s. The number of individuals in state and federal prisons declined until 1970 and then began a slow growth — even as the crime rate continued to climb.
Beginning in the mid-1970s, the incarceration rate began to climb and the crime rate began to flatten out. Toward the end of this period, when incarceration was rising sharply, the crime rate began to drop. It has been falling steadily, year by year, since 1991. The relationships are presented in the table on the next page.
Before we look at the table, note that the decline in violent crime has been sharper than the downturn in property crime. Along with prison population ratios, data for both prisons and jails are graphed from 1980 forward. Persons in prison are incarcerated for periods of more than one year. Persons in jail typically serve one year or less.
Percent Change in Selected Period
| Period | Crime | Prisoner |
| Rate | Population | |
| 1957-1967 | 130.7 | -14.0 |
| 1967-1977 | 162.5 | 35.0 |
| 1977-1987 | 9.9 | 73.0 |
| 1987-1997 | -11.3 | 94.3 |
| 1997-2000 | -16.3 | 7.2 |
The table shows percent change in the official crime rate and in the rate of the prisoner population for four decades and for the final three year period graphed. Thus in the 1957 to 1967 period, the crime rate shot up nearly 131% while people in prison dropped by 14% (per 100,000 inhabitants). In the 1987 to 1997 period, the crime rate dropped more than 11% and the prisoner population shot up nearly 100%.
The table appears to show a societal "reaction lag." Energetic measures to counter the rising crime wave took some time to develop. Eventually it took hold. Statistics are simply photographs of a situation. They do not logically force the conclusion that locking up the bad guys reduces crime — but an inference may be permissible, perhaps. The lag is illustrated by the fact that the 94.3% increase in incarcerations in the '87 to '97 period seems to have "spilled over" into the next period. In the three years between 1997 and 2000, the crime rate dropped more rapidly than in the entire decade before.
We look next at some of the demographics of crime.
Sources: U.S. Bureau of the Census, Historical Statistics of the United States, September 1995 and Statistical Abstract of the United States, 1980, 1990, 1995, 2001. The primary data source cited by these sources are data from the FBI's Uniform Crime Reports (for crime rate) and the U.S. Bureau of Justice Statistic's Prisoners in State and Federal Institutions and Correctional Populations in the United States.
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