We held a seminar with speaker Len Cook on the trends in imprisonment of young Māori men in Aotearoa New Zealand over the past thirty to forty years focusing on analysis of cohorts and age groups.

The likelihood of imprisonment of Māori males aged 30 and older has risen slowly over the past 3 to 4 decades. It has taken some fifty years to see a reversal in the rates of imprisonment of young men. The normalisation of this situation was one of the more enduring consequences of the extreme periods of child custody and incarceration of boys and young men by the State from the mid-1960s to the mid-1980s. These groups experienced some of the highest ever rates of state custody; at the peak up to one in every fourteen Māori boys, youths and young adults was institutionalised through the courts.

Statistician Len Cook takes a fresh look at the existing statistics to discern the trends through the differing lens provided by cohorts, age groups and period analysis. The divergent trends we now see in state custody of younger people are associated with an uncommon history and demographic dynamism that differs with ethnicity. To highlight the limitations of disparity ratios Len will draw on some methods of analysing disparity developed by Florence Nightingale. He will conclude with some insights from his recent inquiries for the future evidence base for the wider social services sector.

Presentation: Divergent futures & the long reach of historical extremes in imprisonment, pdf


Len Cook began a career in official statistics in 1971 and was Government Statistician until 2000 then National Statistician of the UK until 2005. He has also been involved in official statistics in the Pacific and was the chair of the Superu Board until 2018. Len’s most recent work has been on interpreting the institutional counts published by justice sector and child welfare agencies to put a spotlight on the significance of current trends.

This seminar took place on Wednesday 21 July 2021 at Adam Auditorium, City Gallery, 101 Wakefield St, Wellington.

For more information please contact libby.grant@otago.ac.nz.

Equity Health NZ Policy