What if you could track the cost of feeding a family across five decades in a single number?

Stats NZ's food price index for the South Island starts at 1975 and ends at 2024. The latest figure: 15,305. That's not a dollar amount. It's an index number, with 2017 set as the baseline year. But it captures something visceral: the relentless climb in what it costs to fill a trolley, year after year, for half a century.

The recent trajectory tells its own story. In 2020, the index sat at 12,509. By 2024, it had jumped to 15,305. That's a rise of 2,796 index points in four years. To put it another way: the cost of groceries in the South Island rose more between 2020 and 2024 than in many entire decades before that (Source: Stats NZ, food-price-index-regional).

This isn't just about numbers climbing. It's about what those numbers mean for the households living below the Waitaki. A family that budgeted $250 a week for groceries in 2020 would need to find an extra $56 a week by 2024 just to buy the same food. Over a year, that's nearly $3,000 more.

The dataset goes back to 1975, a time when New Zealand's economic landscape looked unrecognisable. No GST. Controlled prices on many goods. A dollar that bought vastly more than today. The index has climbed steadily ever since, with occasional sharp jumps during periods of inflation.

What makes the 2020-2024 period stand out is the speed. Between 2021 and 2022 alone, the index jumped from 12,766 to 13,735: a single-year increase of 969 points. That's the kind of acceleration that forces households to make choices. Do you buy less? Switch brands? Skip meals?

By 2023, the index had reached 15,064. The 2024 figure of 15,305 shows the climb has slowed, but it hasn't stopped. And it never really does. Over 50 years, the trend line points in one direction: up.

This is the story of grocery inflation as lived experience. Every time the index ticks higher, someone in Dunedin or Timaru or Nelson is standing in a supermarket aisle, doing the mental arithmetic, trying to make the budget stretch. The numbers are abstract until they're not.