Even more precisely, CPI tracks what someone has decided the average person would buy, and its basket of products is often tweaked to present more palatable numbers; it makes comparison of prices and inflation across years pretty much impossible.
The real inflation value a person experiences is often much greater than the cooked CPI figures.
> its basket of products is often tweaked to present more palatable numbers
This is a common conspiracy with scant evidence. The tweaks go in multiple directions and are better explained by the decoupling of PPI and CPI (due to longer and more-international supply chains) than conspiracy.
> it makes comparison of prices and inflation across years pretty much impossible
You can decompile the underlying statistics. Enterprises hire in-house economists to do this regularly.
For consumers, I'd say this is pretty selly, as is relying on nonsense like ShadowStats. Comparing value across long periods of time is almost fundamentally a fool's errand. What's an iPhone worth to someone in 1950? Between zero and a commanding fraction of global GDP.
The real inflation value a person experiences is often much greater than the cooked CPI figures.