Below is a slide from a presentation Bill English made to church leaders.
Here's my interpretation.
According to Infoshare, 60,400 children were born in 1990. The numbers on the left chart add up to 62,418. That'll be because some children are added to the birth cohort who were not NZ born but had contact with one of the agencies later eg children of refugees.
Looks like 10,803 had contact with Work and Income by age 5.
3 agencies are depicted: Work and Income, CYF and Corrections (parental connection).
So of the 10,803 children who had contact with Work and Income, 30 percent had a parent in the Corrections system.
The 577 children who had contact with all 3 agencies would cost the state around $270,000 by age 35.
Actually I am surprised the figure is as low as that. Perhaps it hasn't been inflation-adjusted.
Some children had no contact with a state agency before five but still register later costs.
The interesting aspect is that only 14 percent of children who had contact with CYF, CYF and Corrections, or Corrections hadn't been in the benefit system.