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Glossary
Delta HHI
Delta HHI measures the increase in concentration attributable to the deal by comparing HHI before and after the transaction.
Why it matters
Two markets can end with similar HHI levels while the transaction-specific impact remains very different. Delta HHI isolates that impact.
In practice
It is especially useful for prioritising sensitive zones in local or multi-site retail transactions.
Common mistake
Looking only at final HHI without measuring the transaction-specific increase in concentration.
Turn point-of-sale data into usable market share / HHI analysis
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