Central to many intellectual property disputes is an assessment of the degree of similarity of two contested marks. A determination of similarity is fundamentally a subjective decision involving a range of relevant tests, which include consideration of the perception of the relevant consumer and recognition of the existence of degrees of similarity within a spectrum (from high to low).

However, a more objective framework could have a number of advantages, including the potential to quantitatively measure the difference between marks, and providing the possibility to define thresholds up to which IP protection could apply, and build a case-law background offering a basis for greater legal consistency.

This article considers the cases of colour and word marks, and outlines some potential methodologies for quantifying the degree of similarity of marks. The analysis suggests that it should be possible to construct objective similarity metrics which could be applied to IP disputes and potentially incorporated into case law.

The proposed algorithm for word marks takes into account both visual (i.e. spelling) and phonetic (i.e. pronunciation) similarity, and also incorporates a number of additional features of an idealised metric such as down weighting the influence of any final ‘s’, putting greater weight on similarity at the start of the strings, and including elements of ‘normalisation’ relative to the length of the strings—though further ‘tuning’ is likely to be required. It is, however, worth noting that the suggested model takes no account of conceptual similarity (i.e. meaning) and does not attempt to address similarity of associated goods and services classes.

Other future developments might involve efforts to ascertain the likelihood of confusion of marks (rather than just their similarity). One very simple possible basis for this determination—utilising the numbers of results returned by search engines for the marks in question, as a proxy for their overall commonness or prominence—is also discussed in this study.

Finally, it is important to note that the formulations presented in this article are suggested merely as tools to be incorporated into existing approaches and doctrines—which involve a range of additional manual review processes—rather than being intended to replace (on a wholesale basis) the current nuanced and multi-faceted approach to infringement employed by courts and tribunals.

Download the full PDF: Towards a Quantitative Approach for Objectively Measuring the Similarity of Marks