Article dans une revue: While the new European merger regulation makes explicit room for efficiencies, they almost never sway the decision in practice. To some extent, this is because the need to prove that the three cumulative conditions- verifiability, merger-specificity and benefit to consumers – are met is a tough requirement. But this difficulty is compounded by the prevalence of three views which reduce competition authorities' receptiveness to efficiency claims, and which we believe to be mistaken. These views are (i) the idea that efficiencies cannot benefit consumers in little competitive markets, (ii) the idea that savings on fixed costs never benefit consumers, and (iii) the idea that buyer-power induced cost reductions are irrelevant. More balanced presumptions would likely improve the treatment of efficiency claims.