To conduct this analysis we took populations of 19 year old New Zealand residents and gathered all training enrollments at age 19 from Ministry of Education records. From these enrollments we link qualification completions by age 25 and categorize students based on the highest level qualification obtained.
From this population we link through to IRD tax records and calculate median incomes of only those who have active records in a year. Meaning, if a person had moved overseas and had no income in that year they would be excluded from the calculation of the median.
We include income from wages and salaries, business income sources and wages and salaries. Beneficiary income, and rental incomes are excluded.
Income is adjusted relative to the CPI.