Getting a degree can earn you a cool $1.3 million more over your lifetime than leaving school and going straight into work - but the gains vary wildly depending on what subject you study.
New research by Universities NZ confirms that a bachelor's degree in medicine is still by far the most valuable, earning an average $3.5m more than a school-leaver over a lifetime, well ahead of an extra $2.7m for a bachelor of law and an extra $2.2m for a bachelor of civil engineering.
But a bachelor's degree in tourism gives you a paltry lifetime advantage over a school-leaver of just $44,000.
Degrees in personal services, complementary therapies and "other education" (excluding teaching) actually reduce your lifetime income compared with going straight from school to work, after allowing for course fees and time spent studying.
The Herald has used the data to create a calculator showing how much extra you are likely to earn over your working life, depending on your chosen subject and qualification level. It also shows how old you will be when you break even on the extra costs of your study.
The new research, based on 2018 census data, shows that the average advantage of getting a degree over a school-leaver has shrunk by 15 per cent since the 2013 census - from an extra $1,483,000 over a lifetime to $1,263,000.
Ministry of Education research also shows that the financial advantage of higher education has been falling since 2002 because more people are getting degrees and because of big increases in the minimum wage.
The proportion of employed people aged 15 and over with degrees more than doubled from 13.6 per cent in 2001 to 28.5 per cent in 2018.
And after adjusting for inflation, the adult minimum wage jumped by 57 per cent in real terms from $10.50 in 1997 to $16.50 in 2018, expressed in 2018 dollars.
Universities NZ chief executive Chris Whelan said the buoyant job market in 2018 also pulled up incomes for school-leavers, reducing the advantage of getting a degree.
However, that factor is likely to have reversed this year with the jump in unemployment caused by the Covid-19 lockdowns and border closure.
"Degree-holders were relatively unaffected by the higher unemployment in 2013. School-leavers without skills were much more affected," Whelan said.
"It would be interesting to do the same exercise in a year's time, because we are heading into a period of higher unemployment and I would expect to see that gap actually rising again."
In the Universities NZ data, the age when you become better off than a school-leaver assumes that you take the "standard" time off work to study after leaving school - six or 12 months for a level 4 qualification, three years for a bachelor's degree (level 7 on the Qualifications Framework), four years for an Honours degree (level 8), five years for a Master's (level 9) and eight years for a doctorate (level 10).
The analysis assumes that students don't do any part-time work while studying, take out the median student loans for course costs and living expenses, and pay higher taxes after starting work until the loans are repaid.
On that basis, someone with a bachelor's degree would overtake a school-leaver financially by age 24 with a degree in librarianship, by 25 with a degree in computer science, 26 with a civil engineering degree and 28 with a degree in accountancy or medicine.
But people with degrees in business studies, law, most science subjects, social sciences, nursing and teaching would not overtake school-leavers until their 30s.
Those with degrees in low-paying subjects, such as philosophy, literature and creative arts would not break even until their 40s, and degrees in tourism, human welfare (social work) and food and hospitality don't pay for themselves until your 50s.
The income data shown in the interactive is based on the "net present value" of future earnings after deducting the costs of studying. This assumes that you value $1 earned next year at 3 per cent less than $1 earned today, so you value $1 earned in 40 years' time at only about half of $1 earned today.
"The idea is that the lost income for the years spent studying and the fees paid, need to be put in the context of future income that has lower real value - a dollar now should be more of an incentive than the same dollar in 10 or 20 years time," Whelan said.
"In 10 or 20 years' time, I'd like to have at least $2 if I'm going to be asked to give up that dollar now."
Lifetime earnings were calculated by adding the average incomes of people with each qualification who were employed on census day in 2018 in each age group.
On average, people with level 4 qualifications, which include most trades, earned 21 per cent more than school-leavers over their lifetimes after deducting the costs of studying.
People with degrees earned 47 per cent more, those with Honours earned 60 per cent more, Master's degrees earned 58 per cent more and doctorates earned 76 per cent more than school-leavers.
Universities NZ has also used the data to show average earnings for qualifications at each level in each subject for people in their thirties, which may be more relevant to young people embarking on study today.
However other researchers have used different techniques to show differing outcomes. Berl found in 2017 that people with trades qualifications could be roughly equally well off as people with bachelor's degrees by age 65, assuming that both groups bought a house as soon as they could afford it.
Berl economist Mark Cox said his work only counted people with at least level 2 of the National Certificate of Educational Achievement (NCEA), so it compared outcomes for people with similar "innate ability".
"It's not surprising that this [Universities NZ] comparison reveals a lifetime earnings advantage for degree holders, because it compares high achievers with people who might have low innate abilities or who might be disaffected, handicapped etc," he said.
"I am confident that our approach is rigorous and valid because it compared like with like, as far as possible. I also believe that it is better to use longitudinal data where it is available [which we did], rather than cross-sectional data [which Universities NZ did]."