The data are reported by frequency, mean, median, and dispersion. An overview notes that the data aid understanding of how the Illinois sentencing laws, including the Truth in Sentencing statute enacted in 1995, have generated persistent growth in the State's prison population over the past 10 years. The discussion notes that the December 31, 1996 inmate population reached 38,852, an annual rate of increase of 6.9 percent per year since 1977. The correctional institutions were designed to hold no more than 28,200 inmates. The expansion in the number of inmates is largely a consequence of the number and length of murder, Class X, and Class 1 sentences imposed since determinate sentencing began in 1978. Inmates with a life or death sentence, habitual child sex offenders and child sex offenders, and indeterminately sentenced inmates who remain incarcerated also contribute to the continual expansion in population. An escalation in sentences for drug law offenses, particularly for Class 4 possession of a controlled drug, is a recent contributor to the increase in the prison population. Figures, tables, and appended comparison of Illinois sentencing practices