CPI Seasonal Item Aggregation

Aggregation is handled somewhat differently for seasonally adjusted CPI item series. Unlike not seasonally adjusted aggregate item series, which are always constructed from a set of basic indexes, seasonally adjusted aggregate indexes can be created using other intermediate aggregate series. Table 1: CPI seasonal aggregate items shows the items which compose each seasonally adjusted aggregate item.

For example, there are intermediate aggregate items used in the construction of the seasonally adjusted all items less food and energy index which have to be split out according to which are commodities, and which are services, with some subcomponents in services less energy services and others in commodities less food and energy commodities. In cases where intermediate aggregate components used in the construction of the all items less food and energy index are seasonally adjusted, but not all the constituent subcomponent indexes are individually seasonally adjusted, a situation can arise where the seasonal pattern exhibited by the aggregate is different from the seasonal pattern exhibited by the components. Often, this difference is not large enough to be visible at the published level of decimal precision. However, when the overall impact of seasonal adjustment is large, typically in November and December, these differences can grow to a level where they can be observed in the published data.

Download an XLSX version of this table here:

• Table 1: CPI seasonal aggregate items (XLSX)

Last modified date: February 24, 2026