What a catchment area is in competition law
The catchment area is the geographic perimeter within which a store exerts effective competitive pressure. In food-led retail it is the building block of the relevant geographic market: it determines which competitors actually count.
The Authority does not reason with a single radius. It adjusts the size of the area according to store format, population density and the dominant way customers travel.
In dense areas: short zones travelled on foot
In large cities, and Paris in particular, the Authority uses very short catchment areas. Decision 13-DCC-90 (Casino / Monoprix) illustrates this: zones of 300 to 500 metres travelled on foot, with increased substitutability between convenience formats.
The consequence is significant: a few hundred metres apart, a store's competitive environment changes. A credible local analysis therefore requires fine, store-by-store segmentation rather than a uniform radius applied mechanically.
In suburban and rural areas: drive time
Outside dense centres, car travel dominates and the area is measured in drive time. The Authority then reasons in isochrones — typically around 15 to 30 minutes by car for a hypermarket — rather than walking distance.
The choice of isochrone is not neutral: it determines which competitors enter the market-share calculation and, ultimately, the level of overlap between the parties to the transaction.
- §Convenience format in the city: short zone, pedestrian travel.
- §Supermarket: intermediate zone, mixed walking / driving.
- §Out-of-town hypermarket: 15 to 30 minute drive-time isochrone.
Substitutability between formats, not just distance
A catchment area is not only a matter of geometry. The Authority examines whether formats are genuinely substitutable from the consumer's point of view: a hard discounter, a premium supermarket and a drive-through do not capture the same demand.
That is why two nearby stores may belong to different markets, and two distant stores to the same market. The definition follows real demand, not proximity alone.
What it changes for your case
To prepare a notification, the point is to document the chosen area explicitly and justify it against the Authority's practice. A poorly calibrated area undermines the entire market-share calculation that follows.
Before modelling a real transaction in the Pyner platform — isochrones, market shares, HHI market by market — L420 lets you quickly check how the Authority defined catchment areas in comparable cases.