I think their point is that CPI calculations use a single basket of goods for 'everyone' while in reality different people So their example was that if restaur

I think their point is that CPI calculations use a single basket of goods for 'everyone' while in reality different people So their example was that if restaurant food hasn't increased in price by much, but basic groceries have then the 'inflation' seen by different groups may be very different. Another example may be that if average housing costs increase just a bit, but the lowest rents have increased the most then cost of living changes could be significantly different between mid and low income families. I'm not saying either of those examples accurately reflect how things are changing in the US (as I don't have the data to hand), but they are realistic scenarios.