Department of Corrections data shows long-term prisoners served an average of 79% of their sentence before being granted parole, the retiring chair of the Parole Board, Warwick Gendall QC, says.

In the Parole Board annual report to 30 June 2018, Mr Gendall says the public is the public is rightly concerned about the prison population which as of March 2018, exceeded 10,800.

"However, long-term prisoners are serving only a slightly longer proportion of their sentence before being granted parole than they were a decade ago," he says, and notes that in 2008 long-term prisoners served an average of 75% of their sentence before being granted parole.

"The increasing prevalence of gang membership amongst the prison population is likely contributing to this slight increase. There has also been a steady decline in the rate of parolees being re-imprisoned within a year of release. A decade ago, 21% were being reimprisoned within a year. That percentage has fallen to 16% in the latest statistics."

Mr Gendall says these figures illustrate that the Parole Board has been able to select those prisoners who can safely be released on parole, and those who need to remain in prison for further rehabilitation before they can be safely released.

In the year to 30 June 2018 the Parole Board conducted 8,321 hearings, sitting in panels of three, four, or five members. The overall hearing number was slightly up on 7,739 the previous year. In the 2017/18 year the Board also held 177 face-to-face meetings with victims - an all-time high since creation of the Board in 2002.

New Zealand Parole Board, year to 30 June