This would be a cool idea for a service - I would pay for it. Privacy issues aside, it's a shame that transaction data doesn't include itemized information (e.g. grocery bills only show up as one large charge). I'm sure there are many items I regularly purchase that have changed price without me noticing.

Technically many stores provide level-3 data with cc transactions, which include itemized details, but no idea how a consumer would get it. The exchanges give better rates the more details the merchant provides, level 3 being the highest detail and lowest rates so many of the large merchants provide this data. It's one way they avoid paying sign up bonuses on gift card purchases.

If you want to include shrinkflation, it’s going to wind up involving a lot of data entry.

That sounds like a budget, which is indeed a good thing to have but answers very different questions from a broad-based inflation calculation.

if they normalized the budget such that extra things not purchased in previous years is not taken into account, it could be used as a personal inflation measure. Normalizing the budget means you remove any life-style creep that gets in.

This way, you can look at your salary, and determine whether you're gaining income above your own inflation, or not.

Normalizing the budget that way would seem to be incredibly difficult at a personal level.

If I started buying a better cut of steak or more hamburger and less ramen than last year, would I really be able to tease out that difference without an insane amount of record keeping/data entry?

Statistics canada provides a service similar to this https://www150.statcan.gc.ca/n1/pub/71-607-x/71-607-x2020015...

What would I do with that data?