The methodology and data on this site is presented as accurately as I can, but I'm not a statistician and errors may exist. Please do not rely on this data to make policy, make life alerting decisions, or similar.
Data on this site can come from four sources, depending on which product and and summary you're looking at. The four sources are:
This data is published monthly, and data is usually delayed a few weeks (February's data is available in mid-March).
This data is maintained by the Bureau of Labor Statistics, and they are both Price Indexes. A Price Index tracks the average cost of a standard set of goods in a particular category, and is the most often cited metric to track inflation.
The value here doesn't represent the exact cost, but the relative cost. If the CPI increases 10%, though, the average cost of goods in that category have also increased 10%.
This data is used when making most comparisons on the site. It has the most complete data that goes back the furthest, but is also the slowest to update.
This data is the average price of Regular, Premium and Diesel fuel in the US. It's updated Weekly and is the actual average price for fuel, not a price index.
We use this on the Gas overview page to show changes in the last week.
We also crawl the API of a national grocery store chain for the price of a sample of products. For most categories, we sample 3-5 different products ranging from store brand to name brand and get the prices at many store locations.
The same products are sampled across all stores, and the same products are sampled each day. Specific products or the chain we're scraping are not shared as they are immaterial to the data on the page.
This data is collected daily, and the prices exclude promotional or sale prices. The average of these prices is used on product overview pages to show the current price and changes in the last week.
The numbers we share all generally are just the percentage change between the start and end of a time period. The time period may be 6 months, a year, or a week and is called out next to each percentage.
We don't adjust or modify the data in any other way.
This site isn't run by an economist, so inaccuracies (though not intentional) may exist in the calculations or methodology.
It should go without saying, but this website is presented in a good-faith effort to highlight prices, but it's accuracy cannot be absolutely ensured. Errors may exist, data may be old and not fully updated, or other issues may cause the values on the site to not be accurate.
Do not rely on this site to make purchase decisions, investments, other other important decisions.
Not currently. If there's interest, I can make the raw data available via and API.