News ecosystem dynamics in the attention economy of social media

This thesis contributes to the literature on computational social sciences by providing a robust characterization and quantitative assessment of the dynamics shaping the online information ecosystem. Building upon a geographically and temporally extensive dataset covering over 65 million posts from more than 1,000 European news outlets on Facebook, the work investigates how coverage, engagement, and topic salience co-evolve within the attention economy. Grounded in this framework, the thesis addresses three corresponding and complementary research questions that examine, respectively, the supply-side structural dynamics, the demand-side attention behaviors, and the feedback mechanisms linking the two. Each chapter focuses on one of these dimensions, contributing to an integrated understanding of how supply, demand, and interaction jointly shape the evolution of public issues in digital environments. The first chapter uncovers a universal engagement growth pattern across outlets, showing that attention dynamics in the short term are largely independent of outlet size, revealing a highly competitive and erratic informational landscape. Building on this, the second chapter explores viral events as drivers of audience attention, showing that sudden bursts of visibility rarely translate into engagement growth, and also identifying different viral patterns corresponding to distinct collective attention mechanisms. These findings lay the foundation for the third chapter, which develops a data-driven model of the feedback mechanisms of coverage and consumption dynamics over time, showing that user engagement influences the persistence and diffusion of topics, transforming the classical top-down agenda-setting paradigm into a feedback-driven adaptive system. Overall, the thesis proposes an integrated and empirically grounded framework that connects the structural features of information supply with the behavioral dynamics of attention demand, revealing how their continuous interaction redefines agenda-setting processes in the attention economy of social media.