Why retail requires a specific merger-control method
Retail is a special case in merger control because competitive risk is often determined at a very local level. Two transactions that look similar on paper can produce very different effects depending on commercial density, urban geography, travel habits and the actual store formats present in each area.
That means a national or overly aggregated view quickly misses the real pressure points. A robust retail assessment rarely relies on a single metric or a single map. It combines relevant-market reasoning, a credible local perimeter, comparable competitors and enough before/after traceability to rerun the analysis if assumptions evolve.
Start with the relevant market before looking at the numbers
One of the most common mistakes is to jump directly into market-share calculations before clarifying the relevant market. Yet a number only means something inside the economic perimeter where it is interpreted. In retail, that means asking what store formats really compete, how demand-side substitutability works and what geographic granularity is economically defensible.
The right reflex is to document a simple chain of reasoning: which formats are included, which are excluded and why. That step shapes everything that follows, from competitor selection to the size of the catchment area and the way HHI is interpreted.
- clarify the store formats in scope
- define the relevant geographic granularity
- document sensitive exclusions early
Build local market shares that are defensible in a file
A useful local market share is not just a percentage produced from a dataset. It needs a credible catchment area, comparable competitors and a metric that fits the file, such as surface or revenue when that figure is available and robust enough to use.
In practice, the challenge is not only to calculate a share. It is to recalculate it when assumptions move, explain it clearly to a client and place it inside a coherent before/after framework. That reproducibility is what turns a number into an operational asset.
Use HHI to prioritise zones rather than oversimplify the analysis
HHI is extremely useful, but it should not become a shortcut. In multi-site retail transactions, its value often lies in helping teams prioritise the areas that deserve deeper work. Reading HHI before, HHI after and delta HHI together makes it easier to identify potentially sensitive markets, especially when combined with party proximity and limited comparable competitors.
That prioritised reading is essential in larger deals. It avoids over-analysing secondary areas and focuses effort on the local markets that already look structurally tense before the transaction is modelled in full.
Connect due diligence, filing preparation and operational deliverables
A strong retail workflow does not artificially separate exploratory work, competitive due diligence and filing preparation. The same building blocks should move across those phases: stabilised data, explicit assumptions, maps, tables, exports and documented judgement calls.
The more unified that chain is, the faster the team moves. Iterations become cheaper, version divergence decreases and collaboration between deal, legal and advisory teams becomes much smoother.
- stabilise source data before exporting
- preserve methodological judgement calls
- produce reusable deliverables instead of isolated screenshots