Macro Note 42
BLS says the C-CPI-U supplements CPI-U and CPI-W rather than replacing them, and its FAQ says the C-CPI-U uses a formula that reflects substitution across item categories in response to relative price changes. The label marks a different aggregation design, not a simple rename.
Why this note matters
Readers can see `chained CPI` and assume it is just another branding variant of CPI-U. BLS describes a narrower and more technical distinction: the chained index is built to reflect substitution differently and is published on a different scope.
On its chained CPI page, BLS says the C-CPI-U supplements the existing indexes already produced by the agency: CPI-U and CPI-W. That wording matters because it frames the chained index as an additional measure inside the CPI family rather than as the new name for one of the older indexes.
So the first distinction is structural. The chained CPI sits alongside CPI-U and CPI-W instead of simply relabeling one of them.
In its FAQ, BLS says the C-CPI-U employs a formula that reflects the effect of substitution that consumers make across item categories in response to changes in relative prices. The same FAQ also says all C-CPI-U series are published only at the U.S. city average level.
That means the chained index differs not just by title but by the way higher-level CPI aggregation is handled and by the scope of where BLS publishes the series.
Macro commentary often throws around `chained CPI` as if it were just another inflation nickname. BLS's own framing is more precise and more useful for readers who care about methodology.
For Hynexly readers, the practical rule is simple: when someone cites C-CPI-U, ask what methodological point they are making instead of assuming it is interchangeable with CPI-U in every use case.
BLS explains that the chained CPI supplements CPI-U and CPI-W and points readers to the associated methods resources.
Open sourceBLS explains the substitution logic behind the C-CPI-U and states that the published series are available only at the U.S. city average level.
Open source