As inflation hits the supermarket, you’ve probably noticed your regular grocery run has gotten more expensive. The Globe, in collaboration with market research firm Datasembly, is tracking prices of grocery store staples in the Boston area. Each month, we’ll update the prices of everyday items and follow trends over time. The tracker below also offers city-by-city comparisons of grocery prices across dozens of categories.

Here’s a snapshot of recent prices for common products at local supermarkets:

Grocery price index

An index is a useful way of establishing a benchmark to compare dissimilar data points over time, taking into account factors that might otherwise make a comparison difficult (like the price difference between a bag of sandwich rolls vs. a loaf of bread). An index normalizes a dataset, allowing us to pay attention to the rate of change rather than the actual change in values.

The chart below displays a price index developed by Datasembly to easily compare the prices of different categories of grocery store products over time, so we can see which categories are rising or falling the fastest across different US cities. Use the dropdown to compare different categories of grocery items.

See how prices of different grocery categories have risen or fallen since last week

The index values below show price inflation, where October 2019 prices = 100. For example, 119 indicates the price of that product category has risen 19 percent since October 2019. The +/- number denotes the index’s change since last week. Darker colors mean a larger weekly swing.

Methodology

The Globe analyzed data from Datasembly, a firm that collects pricing data from actual supermarkets across the United States.

The rise of online grocery shopping means unprecedented access to hyperlocal, hyperspecific pricing data, Datasembly cofounder and CEO Ben Reich said. Datasembly focuses on sellers that guarantee online and in-store prices are the same, he said. Datasembly pulls its product prices from websites of grocery retailers and averages them.

To create the grocery price index, the company compares its product data to a baseline of data collected in October 2019, which allows for comparison over time and across products or regions.

The index is an attempt to “quantify the intuition around how things are changing,” Reich said.

How we selected the products to track

The Globe spoke with experts to determine common staple items widely available at grocery stores. Then we narrowed down the list to a handful of products, including grains, produce, and meats, taking into account data availability and reliability over time.

Why average prices shown here may be different from what you see at the grocery store

The prices shown here represent averages across many different grocery stores. Grocery prices are constantly fluctuating, and stores routinely offer new promotions. Averages help us keep an eye on broader trends.

Why does one chart say a certain product increased by a different amount than another chart?

Our product-level chart at the top of the tracker shows the Greater Boston area prices for a specific product, while the grocery price index charts display entire broad categories of items.