"There is this huge increase in employment among people over 65, so employers faced with the prospect of employing someone, often for the same sort of work, who is older or a school-leaver, are possibly electing to opt for more mature workers because they are more reliable."
As a share of each age group, employment rates fell in every five-year age bracket below 50, and rose in every age bracket above 50 despite the recession.
One in five over-65s are still in paid work - up from one in seven in 2006, while only one in three teenagers is in work - down from half five years ago.
Waikato University professor of social gerontology Peggy Koopman-Boyden said today's over-65s were "much healthier, more active and more involved" than any previous generation. Compulsory retirement ages have also been illegal under the Human Rights Act since 1999.
"They want to work because they enjoy working, they are participating, they are involved. Why would you give up?" she asked.
Many teenagers are fulltime students who have merely lost part-time jobs. But the numbers who are not in any kind of education, employment or training (NEET) rose from 7.7 per cent of the age group in 2006 to 11.7 per cent in 2009. NEET numbers have since come back halfway to 9.7 per cent.
Mr Johnson said this was partly because a chunk of training funds was switched out of apprenticeships, other industry training and courses for disadvantaged youth, and used to boost universities and polytechnics.
Tertiary Education Minister Steven Joyce said then that much of the money going into industry training was being "wasted" because just over half of all trainees failed to earn any credits in 2009.
But Mr Johnson said shifting the funding to universities meant less training for the most vulnerable.
"It's middle-class capture," he said. "The Government has taken resources out of life-skills and vocational training and put it further up the ladder to the disadvantage of at-risk youth to a degree that it's a ticking time bomb."
Business NZ chief executive Phil O'Reilly said employers were also discouraged from employing teenagers because of a 2008 law change that raised the minimum wage for 16- and 17-year-olds from 80 per cent to 100 per cent of the adult rate after three months or 200 hours in work.
A Labour Department study last year found this change cut the numbers of 16- and 17-year-olds in jobs by between 4500 and 9000 in the subsequent two years. The National Party promised last year to extend the youth minimum wage at 80 per cent of the adult rate until under-18-year-olds have worked for six months for the same employer.
Two sides of the job-seekers' story
The teenager
Jake Flashman, 17, has been willing to work any hours and up to six days a week but has been looking for a job for more than four months.
"Pretty much anything - petrol stations, food places, retail. It's too many people going for the job, and they prefer someone older. They want someone who has had a previous job in the industry," Jake said.
Mostly he did not hear back from those he had applied to.
"I thought I would get one pretty much straight away. I've been surprised at how hard it has been to find a job," he said.
Jake completed Year 13 at Sacred Heart College last year and has been staying with his parents in Remuera.
His friends also had a hard time finding work, though a few settled into fast food work.
Jake has applied for about 15 jobs since October. "There's nothing for secondary school students. You just have to wing it yourself and hope." Jake will be moving to Wellington to study law at Victoria University.
The over-65
Peggy Koopman-Boyden has been researching the experiences of older people for more than 30 years - and has now joined the 65-plus age bracket herself.
"I've worked full time all my life. As I say, I've had a man's career, though I've got two children. I've had the opportunity to work in education all my life. Primary, secondary, tertiary and in the private sector. I like teaching and I also love doing research and communicating the findings.
"Why would you not work? It's for the intrinsic value of contributing to society."
She is a professor of social gerontology at Waikato University. She said she was lucky to have the option of working part-time, but noted that the work of older people included a huge amount of volunteering.
"[Our generation] will live well into our 90s, if not our 100s, so there's a lot of planning that has to go on in terms of what you're going to do and how you're going to support yourself. The best thing you can do is have superannuation. That and good health and lots of friends."