Up here in Canada, the CPI is adjusted from spending surveys:

* https://www.statcan.gc.ca/en/survey/household/3508

When people change their habits in life the CPI is changed to reflect what that life costs. You can see the list of changes going back to 1913:

* https://www.statcan.gc.ca/en/statistical-programs/document/2...

Do you think coal and lard should be included, like they were pre-1956? Or do you think the CPI should try to model reality?

Here's the current list of products that StatCan used for Canada's CPI as of August 2022:

* https://www.statcan.gc.ca/en/statistical-programs/document/2...

Reality is messy, and you cannot take all of it into account, and so you create models approximations (cf. [spherical cow](https://en.wikipedia.org/wiki/Spherical_cow)). But in the words of [Alfred Korzybski](https://en.wikipedia.org/wiki/Map–territory_relation):

* [The map is not the territory.](https://en.wikipedia.org/wiki/Map–territory_relation)

* https://fs.blog/map-and-territory/

Or those of statistician George Box:

* [All models are wrong but some are useful.](https://en.wikipedia.org/wiki/All_models_are_wrong)