"In each case, the numbers were going in the opposite direction between 2008 and 2010."
Teacher vacancies were more or less holding steady, but principals have told Hipkins the positions are getting harder to fill.
"It's a difficult situation for schools at the moment and we know that it will get significantly worse if we don't increase the number of teachers that we're training," he said.
Part of the problem was increasing teacher workloads.
"If you look at policies like national standards - huge increase in teacher workloads without resulting in any increase in young people's educational achievement," Hipkins said.
"I think one of the things that detracts people from wanting to enter teaching is that at the moment. Teachers have been saying this isn't particularly good career to go into."
The Government has removed national standards as part of its effort to reduce workloads and make teachers more like to be "good ambassadors" for the profession, Hipkins said.
He was confident the Government's $9.5 million teacher supply package introduced before Christmas was enough to keep things running smoothly this year, but said more needed to be done to fix future problems.
"It's a shocking failure of planning by the previous National Government that has left an immediate shortage of teachers, but more worryingly, a ticking time bomb for schools as baby boomer teachers retire and too few teachers come through to take over."