Keep the commune identity and name associated with each transaction’s date, then map records to a clearly stated target geography. INSEE’s historical commune records and Code officiel géographique (COG) passage tables help trace changes; a current name or code should not be treated as a stable identity for the whole series. Check the documentation for the specific DVF release before choosing fields or join keys.
Choose the geography your price series will represent
There is no single required way to harmonize DVF transactions after a commune changes. Decide whether the series should follow the commune units that existed on each transaction date or use a fixed later geography, such as current communes. State that choice and the mapping date so readers can interpret the figures.
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| Approach | What it represents | What to watch |
|---|---|---|
| Historical commune geography | Transactions remain grouped by the commune units associated with their dates. | Names, codes, and boundaries may change over the series, so a place may not be directly comparable under one label throughout. |
| Fixed later geography | Earlier transactions are mapped to a chosen later geography. | Several predecessor communes may need to be combined; document the correspondence and the treatment of unmatched or ambiguous records. |
INSEE provides passage tables for correspondence between commune geographies. They are a starting point for constructing a mapping, not a prescribed DVF price-analysis method. [INSEE: Geographic-administration resources and passage tables]
Build a dated commune crosswalk before aggregating
- Identify the DVF release. Record its vintage, the transaction-date interval, and the commune-related fields you intend to use. Confirm field definitions, formats, and coverage in that release’s own documentation before coding. The reviewed DVF interface supports selecting a commune and mutation date, but that does not establish the schema or coverage of a downloadable release. [DVF interface]
- Preserve the source record’s geography. Keep the source commune code, source label, transaction date, and the chosen COG vintage in your working data. Retain the original values rather than overwriting them with a current label.
- Check the official history for the relevant dates. Use INSEE’s historical commune records to identify name changes, creations, disappearances, and department changes. The historical record describes these events since 1943; the page refers to the COG as of 1 January 2026. [INSEE: Historical commune records]
- Map to the declared target geography. Use the relevant COG passage table to establish which historical units correspond to the target units. Inspect the correspondence for the specific communes and dates in your series rather than assuming every change is a one-to-one code substitution. [INSEE: Geographic-administration resources and passage tables]
- Aggregate only after mapping. For a fixed later geography, combine predecessor communes only where the correspondence supports that mapping. Keep records with unresolved or ambiguous correspondence visible and explain how you treated them.
Keep names, codes, and vintages distinct
A commune name is useful for checking and presenting results, but it is not a durable identifier across administrative changes. Likewise, a code should be interpreted within its relevant geographic vintage rather than assumed to identify an unchanged area for every year in the series. INSEE publishes annual COG vintages from 1999 through 2026 and historical commune code-name pairs since 2021; its COG page was last updated on 24 February 2026. [INSEE: Code officiel géographique]
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INSEE’s displayed count of 1,406 commune name changes is a filtered page count for the 2026 COG reference. It is not a count of mergers, nor evidence of any effect on transaction prices. [INSEE: Historical commune records]
Show what the mapping changes in the results
Administrative relabeling alone does not demonstrate a change in property prices. Compare the consequences of your chosen geography and make the mapping’s effect auditable. Useful checks include:
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- Compare a historical-geography series with a fixed-geography series where both are meaningful.
- Identify many-to-one mergers and list which predecessor communes contribute to each later commune.
- Report transaction counts and date coverage after mapping, so gaps or shifts in the analyzed records are apparent.
- State how unmatched and ambiguous records were handled rather than silently dropping or assigning them.
Keep tax and cadastral guidance in its lane
DGFiP guidance on territorial boundary changes concerns property-tax valuation: under the cited rules, valuations established for each former commune may remain unchanged until the next general revision. That is tax context, not a method for harmonizing observed DVF transaction prices. [DGFiP: Fiscal treatment of territorial boundary changes]
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