The way CPI is calculated is complex, but they do try to account for substitution and quality changes: https://www.bls.gov/cpi/factsheets/common-misconceptions-

The way CPI is calculated is complex, but they do try to account for substitution and quality changes: https://www.bls.gov/cpi/factsheets/common-misconceptions-about-cpi.htm https://www.bls.gov/cpi/factsheets/common-misconceptions-abo... See "When the cost of food rises, does the CPI assume that consumers switch to less desired foods, such as substituting hamburger for steak?" and "Is the use of "hedonic quality adjustment" in the CPI simply a way of lowering the inflation rate?".