1. Where a quota authorisation that has not been returned or covered by a corresponding sworn declaration pursuant to Article 12 remains unused at the end of quota period n-1, the importer's import ceilings for the product group concerned during quota period n+1 shall be reduced by the amount proportional to the size of the unused quota authorisation.
2. The reduction referred to in paragraph 1 shall be calculated as follows:
R i = ΣU i /ΣΑ i
where:
‘R i ’ represents the reduction applicable to the import ceiling of importer i, for the product group concerned, during quota period n+1;
‘ΣU i ’ represents the sum of unused quantities covered by quota authorisations for the product group concerned granted to importer i during the quota period n-1;
‘ΣΑ i ’ represents the sum of the quantities covered by quota authorisations granted to importer i, for the product group concerned, during the quota period n-1.]