6 Weeks of NZ Shelf Prices: What Actually Moved

Groceries are said to be going up all the time. I have 10 readings of the same products at the same supermarket, taken between 30 July 2026 and 7 September 2026, and that is not what the shelf did.

What is being counted

Since 30 July 2026 each row of the index has been pinned to a specific product code rather than looked up by search, so a reading is the same jar this week as last week. Before that date, a change in the number could just as easily have been the crawler picking a different brand.

The readings are not evenly spaced — they land on 30 July 2026, 2 August 2026, 3 August 2026, 10 August 2026, 12 August 2026, 17 August 2026, 24 August 2026, 5 September 2026, 6 September 2026, 7 September 2026 — because a point is only recorded when the shop's own column date moves.

Two things are deliberately not in here. These are regular shelf prices: when an item is on special the index records the ordinary price, because an index that drops every time something is promoted reports deflation instead of prices. And it is one chain's online shop, not a basket of stores.

8 of 16 did not move at all

Across the whole window, these never changed price by a single cent: Bagels 4-pack, Canned Tuna (185g), Cheese Block (500g), Cucumber, Eggs (12-pack), Pasta (500g), Rice (1kg) and Sliced Chicken (200g).

That list is not exotic. It is the shelf-stable half of a lunchbox — the tins, the block, the dry goods — and over 6 weeks not one of them changed by a cent.

What did move

8 items moved, and 6 of those moved exactly once — one step, then flat again. That is a different shape from the one the phrase "prices keep going up" suggests. The exceptions are Apples (1kg) and Lettuce, which changed 3 times each and are both produce sold by weight.

The basket

Adding the 16 tracked items together: $86.71 at the first reading, $87.30 at the last. A change of +$0.59, or 0.7%.

4 items ended higher, 4 ended lower, 8 ended where they started. The movement did not cancel out because it was small — it cancelled out because it went both ways.

What I took out, and why

4 rows changed specification during the window and are excluded from every number above. They went in as Cherry Tomatoes (250g), Hummus (200g), Peanut Butter (375g), Wraps 8-pack, and they now read Cherry Tomatoes (180g), Hummus (220g), Peanut Butter (380g), Wraps 6-pack — each re-pinned to a product both chains actually carry. Counting those as price movements would be measuring my own spec sheet, not the shelf.

This is the same discipline the specials work needed. Over the weeks of mailers I have logged, the number of promotions per week appears to roughly triple — and the cause is that I started entering whole flyers instead of individual finds. It is a change in me, not in the shops, which is why the specials analysis counts how many weeks an item appears rather than how many promotions there were.

What I would not claim

6 weeks is short, and a 0.7% move over that window is not an inflation figure. It is one basket at one chain.

A price that did not change between two readings could still have moved and moved back in the gap — the longest gap here is 12 days. And because specials are excluded by design, an item listed above as unchanged may well have been half price for a week. What the specials actually do to a lunchbox bill is a separate question with a separate answer.

Every reading behind this is on the NZ Lunchbox Price Index page, published under CC BY.

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