One of the most controversial aspects in the recently adopted U.S. horizontal merger guidelines has been the “downgrading” of market definition and market shares in the analysis of differentiated products mergers. Observers have argued that the guidelines not only create too much agency discretion and flexibility at the cost of consistent analysis and predictability, but also undermine international consensus and set a bad example for other jurisdictions. The note considers that, on the contrary, the U.S. agencies’ approach to differentiated products mergers is consistent with the approach of other leading competition authorities and will likely shape international consensus in merger review. It appears unlikely that this approach will reduce analytical rigor in merger review and lead to more aggressive merger enforcement with an increased number of mergers that competition authorities seek to challenge.