HARRISBURG, Pa. (AP) — The number of inmates in Pennsylvania’s prison system is continuing to decline, with the population last year falling by about 860 prisoners to fewer than 48,500.

The Wolf administration said Monday the 2017 drop represents the fourth straight year that the total inmate population has gone down. Administration officials call last year’s decrease the largest on record.

Pennsylvania ended last year with about 3,300 fewer inmates than five years earlier.

Officials say significant factors include dropping crime rates, diversions of technical parole violators and a state Supreme Court decision that threw out many of the state’s mandatory minimum sentences.

Parole violator admissions fell by more than 10 percent last year.

The dropping prison population prompted the Wolf administration to close Pittsburgh State Prison last year.