While there are several difficulties in projecting future prison populations, it is believed that the guidelines will have minimal effects on future prison populations. However, significant growth in Federal inmate populations is expected over the next 10 to 15 years due to increased prosecutions and convictions, reduced use of probationary sentences, the mandatory minimum penalties required by the Anti-Drug Abuse Act, and increased sentences required by career offender provisions. Based on population estimates of 92,000 to 118,000 in 1997, it could cost several billion dollars to build prisons necessary to prevent overcrowding. In addition, this increased population could add as much as $1 billion a year to the cost of inmate custody, care, and rehabilitation programs.