system
A chat on subreddit /r/wallstreetbets
human
Owner occupied housing (mortgaged) has been excluded from the CPI since 1981. That was the last time interest rates increased significantly. Housing rent is included, but on a national basis this isn't always very instructive.  

edit: previously just stated housing.
gpt
This isn’t entirely true. About 1/3 of the cpi is housing related for example rent, owners equivalent rent, and utilities. Some housing however is classified as investment and is excluded.