The latest week
Week of 28 Sep 2026
The method
Like-for-like prices, chained week on week
The same basket, every week
Every week Pricer re-prices the same groceries at each supermarket, compares them with the week before, and chains those weekly changes back to the base week of 20 Apr 2026. Because only identical products are compared, the index measures pure price movement, not changes in what happens to be on the shelves.
What counts as a match
A product only counts when its price was checked in both weeks. Anything not checked is left out rather than assumed unchanged, and readings that jump more than fourfold are treated as errors. Each category needs at least 10 matched products at a supermarket before it produces a number at all.
From prices to one number
The matched price ratios are combined with a geometric mean (the Jevons formula, the same approach Stats NZ uses for the Food Price Index), then categories are weighted by their share of a typical grocery spend using Stats NZ's 2024 food price weights. The overall figure weights the 4 supermarkets by their share of grocery sales.
Pricer's index is built from tracked shelf prices and is not an official statistic. Supermarkets joined the index as their price data came online, so each one is measured against its own starting week.
One product, worked through
Real prices from the latest week
1. Its price in both weeks
Each supermarket's price this week is divided by its price last week. That ratio is the product's price change. Where a supermarket prices by zone, its price is a geometric average across those zones, weighted by how many stores each zone covers.
| Supermarket | Week of 21 Sep 2026 | Week of 28 Sep 2026 | Ratio |
|---|---|---|---|
| FreshChoice (Epsom store) Chain price | $999 | $900 | 0.9009 -9.91% |
| New World 38 price zones | $970 | $970 | 1.0000 No change |
| Pak'nSave 57 price zones | $910 | $847 | 0.9308 -6.92% |
| Woolworths 1 price zone | $939 | $850 | 0.9052 -9.48% |
2. Into its category
At each supermarket, this ratio joins every other matched Butter & Margarine ratio. Their geometric mean is the category's change for the week, and the category's index moves by it.
3. Into the basket
Butter & Margarine belongs to Stats NZ's Oils and fats class, weight 0.36, or 2.7% of the grocery basket. That weight is shared across the class's 2 categories by how many products each one has. Each supermarket's index then moves by the weighted change across every class, and the overall index by the weighted change across supermarkets.
Supermarkets
When each one joined, and how much it counts toward the overall index
| Supermarket | In the index from | Matched last week | Market share | Index weight |
|---|---|---|---|---|
FreshChoice (Epsom store)
|
20 Apr 2026 | 9,596 | Estimate 3% | 3.9% |
New World
|
20 Apr 2026 | 18,344 | Estimate 22% | 28.6% |
Pak'nSave
|
20 Apr 2026 | 20,635 | 25% | 32.5% |
Woolworths
|
20 Apr 2026 | — | 27% | 35.1% |
Market shares for Woolworths and Pak'nSave are from the Commerce Commission's Annual Grocery Report 2024. It does not publish New World or FreshChoice separately, so their shares are estimates. Index weight rescales those shares to the supermarkets we track, and each supermarket is measured from its own first week.
Category weights
Stats NZ's 2024 food price weights, and the categories each one covers
| Stats NZ class | Weight | Share | Our categories |
|---|---|---|---|
| Soft drinks, waters, and juices | 1.63 | 12.1% | Soft Drinks Juice Water Cordials & Mixers Sports & Energy Drinks |
| Confectionery, nuts, and snacks | 1.45 | 10.8% | Chips & Crisps Chocolate Lollies & Sweets Muesli Bars Nuts & Trail Mix Popcorn & Rice Cakes |
| Vegetables | 1.15 | 8.5% | Vegetables Salads & Herbs Fresh Herbs Organic Produce Frozen Vegetables |
| Fruit | 0.94 | 7.0% | Fruit Frozen Fruit |
| Preserved, prepared, and processed meat | 0.86 | 6.4% | Deli Meats Sausages & Bacon BBQ & Marinated |
| Other grocery food | 0.81 | 6.0% | Canned & Tinned Soup & Stock World Foods Ice Cream & Desserts Frozen Pizza & Snacks Baby Food |
| Beef and veal; mutton, lamb, and hogget | 0.70 | 5.2% | Beef & Lamb Mince & Burgers |
| Coffee, tea, and other hot drinks | 0.57 | 4.2% | Tea & Coffee |
| Bread | 0.56 | 4.2% | Bread Rolls & Buns Wraps & Flatbread |
| Fresh and preserved milk | 0.55 | 4.1% | Milk |
| Poultry | 0.52 | 3.9% | Chicken & Poultry |
| Cakes and biscuits | 0.50 | 3.7% | Baked Goods & Cakes Cakes, Muffins & Desserts Fresh Biscuits & Slices Biscuits & Crackers |
| Fish and other seafood | 0.47 | 3.5% | Seafood Frozen Meat & Seafood |
| Food additives and condiments | 0.47 | 3.5% | Sauces & Condiments Spices & Seasonings Spreads & Honey |
| Cheese | 0.38 | 2.8% | Cheese |
| Oils and fats | 0.36 | 2.7% | Butter & Margarine Oils & Vinegars |
| Eggs | 0.32 | 2.4% | Eggs |
| Pasta products and other cereal products | 0.28 | 2.1% | Pasta, Rice & Grains Noodles & Asian Baking |
| Yoghurt | 0.24 | 1.8% | Yoghurt |
| Pork | 0.21 | 1.6% | Pork |
| Breakfast cereals | 0.20 | 1.5% | Cereals & Oats |
| Pastry-cook products | 0.16 | 1.2% | Pies & Savouries Sweet Pastries & Donuts Frozen Pastry & Bread |
| Other milk products | 0.14 | 1.0% | Cream & Sour Cream |
Weights are each class's percent of the CPI basket at December 2024 prices. Restaurant meals and ready-to-eat food are left out, so the shares add up to the grocery part of the basket only.
Against Stats NZ
Monthly change in our overall index next to the official figure
| Month | Pricer Grocery Index | Stats NZ food, excluding restaurant meals |
|---|---|---|
| May 2026 | +0.42% | +1.02% |
| June 2026 | +0.93% | +0.69% |
| July 2026 | +0.45% | +0.08% |
| August 2026 | +0.33% | +0.26% |
Stats NZ figures from Selected price indexes: August 2026. Our index tracks shelf prices online and is not an official statistic, so expect the two to differ month to month.
