The cumulative effects theory consists in taking into consideration when assessing anticompetitive effects, not only the agreement at issue, but all the parallel agreements binding other suppliers to their respective distributors on the market concerned. The doctrine is only subsidiary in nature and, according to the Commission, only plays a role when an agreement does not meet the appreciable effect condition. This now contains two strands. Firstly, the supervisory authorities verify whether a series of similar agreements have as their effect the closing-off of access to the market concerned. It is irrelevant that the agreements would not individually be likely to appreciably restrict competition due to their effects remaining below the threshold defined by the Commission. Secondly the cumulative effect theory can only apply to agreements that significantly contribute to a cumulative foreclosure effect resulting from a set of identical agreements.

Assessment of the sealing-off effect, which involves establishing evidence of real, concrete market access possibilities, takes account of the number and size of operators present, the degree of market saturation and customer loyalty to existing brands. The existence of similar exclusive purchasing or supply agreements or selective distribution agreements on the same market is therefore liable to seal off market access.

First developed by the Court of Justice, the significant contribution to the cumulative effect criterion has now been endorsed by the Commission. The Notice on agreements of minor importance provides that agreements entered into by distributors or suppliers with a market share not exceeding 5%, do not significantly contribute to the cumulative market foreclosure that would result from agreements concluded by several suppliers or distributors. To assess an agreement’s contribution to market foreclosure, the supervisory authorities take into account the effect produced by the supplier’s entire network. The supplier’s market position, the degree of apparent dependence of sales outlets and the nature and duration of restrictive agreements are all factors used to assess how significant a contribution an agreement to the cumulative effect makes. On the markets for fuel distribution or beer supply, only those agreements that exceed the average duration for agreements habitually concluded on the market are found to be anticompetitive. Sometimes, the supervisory authorities may break down the network of a specific supplier in order to focus on only those agreements that contribute significantly to market foreclosure.