Engagement on social networks is a complex concept, in which many interconnected, difficult-to-assess components interact. It is precisely this complexity which motivated this work, which proposes a composite index as a tool to measure engagement. Using TOPSIS, a multicriteria method that bases its ranking on minimizing the distance to the ideal point and maximizing the distance to the anti-ideal, a mix of indicators based on two approaches is used: the tweet approach and the follower approach. The former reflects engagement based on user production, and the latter measures engagement by popularity. This index was applied to a group of Social Media Influencers and a general ranking was obtained, as well as a ranking by each approach to measuring engagement. A comparison of the rankings generated by the different approaches shows the suitability and pertinence of both, as it is confirmed that they measure different aspects, and that both are needed to offer a holistic view of the engagement generated by a user on Twitter; this is a new finding compared to prior studies, which only focused on one approach or the other.
