How much cheaper will groceries be under KiwiMart? The Greens won’t say

A big number with a missing answer

The Green Party’s KiwiMart proposal, launched on 6 September as the centrepiece of an Affordable Kai policy costing more than $6 billion over four years, would compel Foodstuffs and Woolworths to divest 120 stores and two distribution centres into public ownership. The bill is $2.8 billion, split into $1.3 billion for acquisition and $1.5 billion to capitalise the new entity, which would launch with 15 percent market share.

That is a serious commitment of public capital and a serious use of state power to seize private assets. So the obvious question, put to co-leader Chloe Swarbrick on Morning Report, was how much cheaper groceries would actually be. She wouldn’t say. “Politicians are not economists,” she said, arguing that defining excess profit is “best left to the independent experts at the Commerce Commission.”

The problem is real, which makes the vagueness worse

The Greens are not inventing a crisis. The Commerce Commission’s June 2026 grocery report found the market remains 82 percent concentrated, exceeding 90 percent in some regions, with margins and profitability largely stable, a sign competitive pressure is not building. Stats NZ recorded food prices up 4.6 percent in the year to January 2026, meaning grocery inflation has re-accelerated after three years of reform. Swarbrick framed it in stark terms on launch day, accusing the duopoly of taking “about a million dollars a day in excess profit out of our shopping baskets.”

When a diagnosis is that specific, voters and businesses are entitled to a prescription with a dose on the label. Instead the mechanism is to hand the job to a regulator that has existed since 2022 and hasn’t yet moved the needle. The Commission’s own report concedes it will likely take several years to see a meaningfully more competitive market.

A 15 percent player can’t buy like a 40 percent one

This is where the policy runs into the actual economics of grocery retail. The $6 billion in rebates, discounts and payments flowing between the major retailers and their suppliers each year is 26 percent of combined retailer sales revenue. That is the machinery through which scale translates into buying power. Every FMCG brand, food producer and logistics operator negotiates inside it.

A new entrant at 15 percent share would lack the purchasing muscle to match those terms, meaning its cost base would be structurally higher than the incumbents from day one. Swarbrick’s Kiwibank comparison, a “self-sustaining and commercially viable competitor”, flatters the plan. The marginal cost of an extra bank deposit is near zero. The marginal cost of running perishable inventory across island logistics and labour-heavy stores is not.

The break-up numbers cut the wrong way

The research that exists points to caution. A 2022 Cognitus cost-benefit analysis estimated a central net benefit of just $0.5 billion, with a range running from $4.6 billion of benefit to $3 billion of net cost, and smaller retailers’ collective share only doubling from 5 to 10 percent by 2042. A 2023 MBIE analysis cited by The Spinoff put the cost of forcibly breaking up the chains at as much as $3.8 billion over 20 years, mostly through lost economies of scale that would push distribution costs and prices up.

The Spinoff also identified the barrier no acquisition fixes. New Zealand’s shortage of grocery competition is fundamentally a shortage of viable land and permissive zoning. Buying existing stores relabels the market rather than expanding it.

What the government tried and why it matters

Swarbrick is right that begging an offshore third player has failed. Both major parties spent three years courting an international chain that never arrived. The most credible line item in the Greens’ package is arguably the more than $100 million to boost Commerce Commission powers, a mandatory pricing accuracy code and an extension of the Consumer Data Right to supermarkets. Those are enforcement and transparency tools, and they carry no $2.8 billion asset seizure risk.

That is the tell. The Greens are relying on the regulator to deliver the price discipline, which raises the question of what the $2.8 billion supermarket actually buys that stronger regulation does not. Until someone can say how many cents come off a litre of milk, KiwiMart is a promise of competition without the one thing competition is supposed to produce, a lower price you can name.

Sources

• Greens can’t say how much cheaper KiwiMart would be, say government won’t set prices (2026-09-07)
• Greens vow to break up supermarket duopoly, set up publicly owned ‘KiwiMart’ (2026-09-06)
• Greens propose new supermarket chain in bid to cut grocery costs (2026-09-06)
• Greens pledge publicly owned supermarket chain called KiwiMart (2026-09-06)
• Greens announce Kiwimart; a state-owned supermarket to take on duopoly (2026-09-06)
• 2025 Annual Grocery Report – Commerce Commission (2026-06-02)
• Annual food prices increase 4.6 percent – Stats NZ (2026-02-17)
• Why New Zealand can’t get a third supermarket chain – The Spinoff (2026-04-28)
• Provisional supermarket divestment cost benefit analysis – Cognitus (2022-10-04)