Being in the wrong KiwiSaver scheme has been compared to throwing away a first division-winning Lotto ticket.
More than 400,000 Kiwis continue to invest in default KiwiSaver funds, which are more conservative. They're much less likely to lose money when the market tanks, but the long-term returns are generally lower than more aggressive schemes.
In total there are around 20 retail KiwiSaver schemes, of which nine are designated as default. With a review expected next year, there are calls to get rid of the conservative funds.
Pocketwise co-founder Binu Paul says they may be good for people close to retiring, but not the majority.
"If you consider someone who's a 30-year-old, started investing in KiwiSaver when it started... you're roughly missing out on $10,000 to $12,000 so far. But that exponentially grows by the time you retire to roughly anywhere between $300,000 to $1 million."
Mr Paul says providers should move their members into more appropriate funds.
"The intention back in 2007 when it launched was the fact not everyone would have an idea of what to do with it. Workplace super is pretty new to New Zealand - we're probably one of the most recent countries to launch workplace super, as opposed to in the US which started in the 1960s, the UK around the same time, and Australia in 1992.
"The idea was this would be a short-term parking space - you have a set of default funds that if you didn't make a decision, your money got invested in. But people are starting to use these for long-term parking.
"What's essentially happening is default funds on average have been earning around 5 percent over the last 10 years, whereas balanced and growth funds have been averaging around 7, 7.5 percent. A 2 percent difference over a 30-year period, you're talking hundreds of thousands of dollars."
That's thanks to exponential growth. For example, if a 35-year-old had $50,000 in a conservative KiwiSaver fund earning 5 percent, and put no more money into it, by the time they're 65 it'll be worth $216,100. But if they put the same amount of money in a growth fund earning 7.5 percent, it would be $437,750 - more than twice as much.
With recent wobbles in the world stock markets, Mr Paul says people invested in growth funds need to resist the temptation to pull their money out.
"The worst thing you can do is get out of your fund when it's lost money - you're crystallising that loss. But if your timeframe is much longer, it's going to recover."
Other suggestions to improve KiwiSaver include shortening the contributions holiday period from five years to 12 months to encourage more saving, allowing workers over 65 to still get their employer contribution, and making KiwiSaver compulsory when starting your first job.