The ranking of goods and services by the providers of online intermediation services has an important impact on consumer choice and, consequently, on the commercial success of the business users offering those goods and services to consumers. Ranking refers to the relative prominence of the offers of business users or relevance given to search results as presented, organised or communicated by providers of online intermediation services or by providers of online search engines, resulting from the use of algorithmic sequencing, rating or review mechanisms, visual highlights, or other saliency tools, or combinations thereof. Predictability entails that providers of online intermediation services determine ranking in a non-arbitrary manner. Providers should therefore outline the main parameters determining ranking beforehand, in order to improve predictability for business users, to allow them to better understand the functioning of the ranking mechanism and to enable them to compare the ranking practices of various providers. The specific design of this transparency obligation is important for business users as it implies the identification of a limited set of parameters that are most relevant out of a possibly much larger number of parameters that have some impact on ranking. This reasoned description should help business users to improve the presentation of their goods and services, or some inherent characteristics of those goods or services. The notion of main parameter should be understood to refer to any general criteria, processes, specific signals incorporated into algorithms or other adjustment or demotion mechanisms used in connection with the ranking.
