Cumulation of origin requires minimum value addition in exporter and aggregate across parties for preferential treatment. Rule 8 provides that for a product meeting rule 5(b) and exported by a Contracting Party using materials, parts or products originating in the other Contracting Party, the value addition in the exporting Contracting Party must meet a minimum proportion of the f.o.b. export value, subject to the condition that the aggregate value addition across the Contracting Parties meets a higher proportion of the f.o.b. export value. Cumulation counts only inputs that have already acquired originating status in one Contracting Party when used in the other for preferential treatment.