[totalZero]

Consumer price inflation measurement lags because the basket composition changes. True inflation is likely far higher than CPI inflation because of this market basket recomposition problem. BLS doesn't update the market basket instantaneously; it lags by about two or three years. Thus, when discontinuous shifts in consumer behavior aggressively drive spending out of certain areas (eg airfare, tuition, elective surgery, rent) and into other areas (eg autos, fuel, new construction, computers), those shifts are underrepresented because deflation of the former is weighted more heavily than inflation of the latter.

Any time there is price dispersion within the goods and services of the market basket, it's likely that the basket composition itself is changing too. CPI has no way of responding quickly to this change.