KiwiSaver provider Milford Asset Management says the retirement scheme shouldn't be made compulsory.
Milford's executive director and Weekend Herald columnist Brian Gaynor says he disagrees with calls from KiwiSaver founder and former Finance Minister Sir Michael Cullen to make the scheme mandatory.
"We think it'll make fund managers a bit complacent," Gaynor said.
"If everyone is compelled to contribute, it takes a lot of the competitive onus away from fund managers. Having a voluntary scheme keeps us more on our toes, having to perform better."
While many more people signed up to scheme than originally expected, Gaynor said only 10 per cent of people's funds are invested in the New Zealand sharemarket.