New data shows which KiwiSaver providers have been adding and losing members - and one says it's a wake-up call to big operators that they can't be complacent.

MJW has released its latest KiwiSaver Market Review, which also shows wide variation in the average balance of schemes, from less than $30,000 to more than $180,000.

It shows, at March this year, there was $138.7 billion invested in KiwiSaver by 3,440,466 members, who paid an average $287 in fees in the year.

ANZ remained the biggest provider, with ASB in second, and Fisher Funds in third. Milford overtook Westpac for fourth place and Generate moved past AMP into sixth place.

The biggest winners in terms of investment asset growth over the year to March were Milford, Generate and Sharesies. Milford had the strongest growth in assets under management over the year, at $3.4b growth. It was followed by ASB at $2.1b.

Milford was up more than $10b over five years to March.

But in proportionate terms, the strongest growth was seen from newcomers Sharesies and Kernel. Sharesies grew 162% and Kernel 128%.

In terms of member numbers, Milford had the largest increase over the year, at 37,383, followed by Generate at 24,320. But Sharesies grew member numbers by 128% and Kernel by 95%.

ANZ lost 16,490 members over the year and Westpac 8552. In percentage terms, Pie dropped 10%.

Milford and Simplicity had added around 130,000 and 100,000 members respectively over the last five years. Milford also featured as one of MJW's strongest performers over the longer-term, although it had slipped this year.

Melville Jessup Weaver (MJW) principal Ben Trollip said brand awareness was a big driver of growth of funds.

"Whether that is built of strong long-term performance - like Milford or Generate - or a high degree of control and flexibility - like Sharesies and Kernel. Also, it feels like KiwiSaver advertising is become more prevalent. I've seen some statistics suggesting transfers are high which would suggest consumers are becoming more engaged and making changes if they're unhappy with their current provider."

KiwiWRAP had the highest average balance at March, at $184,600 but it only had about 1600 members and was one of the smallest providers. MAS at $107,600 and Craigs at $100,900 had relatively high average balances, too. Westpac and BNZ were among those with average balances well below the overall national average of about $40,000.

Overall, 61.4% of members were contributing according to MJW but that was more than 80% of Kernel, KiwiWRAP and NZ Defence Force members.

Fees as a percentage of assets were highest in AE, at 1.84%, according to the data, and Christian KiwiSaver, at 1.4%. Generate was at 1.32%.

There were now almost 40 KiwiSaver providers. Trollip said it was surprising that there had not been consolidation of the market over time.

"If I was to speculate, I'd guess the barrier to entry remains relatively low and KiwiSaver still looks like an attractive market given the strong growth overall. It does look like we will see fall in the number of individual schemes this year with, for example, Fisher Funds going from three to one."

Kernel founder Dean Anderson said the growth in some schemes showed that a growing portion of the market was moving from incumbents to schemes that were investing and innovating to deliver more transparency.

"It's pretty clear, you can see that those that have kind of forgotten about KiwiSaver and their customers and basically let it stagnate for the past sort of five years are now seeing a rise of customers migrate away from those offerings."

He said because the data was only until March, it potentially understated the effect of market moves since then. "This is very much an ongoing and accelerating trend."

He said being cheap was not enough on its own to win clients. Westpac and MAS were among the cheapest in their categories, delivered top-five returns, and still lost members. "Simplicity is the cheapest or near-cheapest everywhere and added about 11,000 members, but its growth came largely from default status and its 'disrupter' brand, not visible outperformance."

Average Kiwisaver balances by company at March 2026

AE: $28,400

AMP: $56,100

ANZ: $33,000

ANZ Default: $56,100

ASB: $40,800

BCF: $27.200

BNZ: $27,900

Booster: $32,400

Christian: $54,200

Craigs: $100,900

Evidential: $68,800

Fisher Funds: $37,600

Fisher Funds Plan: $31,700

Fisher Funds Two: $59,100

Generate: $43,700

GoalsGetter: $74,000

Hive: $29,700

InvestNow: $71,500

JMI Wealth: $71,600

Kernel: $50,600

KiwiWRAP: $184,600

Koura: $45,200

Maritime: $74,800

MAS: $107,600

Mercer: $61,100

Milford: $79,700

NZDF: $60,300

NZ Funds: $45,000

OneAnswer: $59,600

Pathfinder: $46,700

Pie: $39,500

QuayStreet: $70,600

SBS: $39,300

Sharesies: $32,100

Simplicity: $39,700

Summer: $74,600

SuperEasy: $60,500

SuperLife: $31,100

Westpac: $30,700