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Rebase / Base-Year Converter
Convert an index value from one base year to another using the splice-point conversion factor, for when a provider rebases or discontinues a series.
A manual one-off conversion. The product chains rebased successors automatically so the mechanism never breaks mid-term.
Rebase / Base-Year Converter, explained
Why does an index change its base year?
Statistical agencies periodically reset an index to a more recent base period (e.g. 2015=100 becomes 2021=100) so the reference point stays current. Values published under the old base need a conversion factor before they can be compared against values published under the new base.
How is the conversion factor calculated?
At the splice point (the one date where both the old-base and new-base values are published for the same period), the conversion factor is the new-base value divided by the old-base value. That single factor rescales every historical old-base value into new-base terms.