Intermedia Agenda Setting Between Social and Traditional Media: A Comparison of Taiwan and U.S. Coverage of the Air Pollution Issue

Using three years of newspaper and social media data (August 2019 to July 2021) from Taiwan and the United States, we tested intermedia agenda-setting (IAS) effects to examine how the salience of the air pollution issue and its attributes transferred between newspapers and social media. We focused on three attributes—health-related topics, negative tone, and present focus. Applying time-series models, moderated by real-world air quality indicators, we found that social media exerted a stronger influence on newspapers at the first level in the U.S. challenging assumptions of legacy media dominance. Reciprocal IAS relationships emerged at the first level in both countries. At the second level, these reciprocal relationships were highly context-specific: traditional media exerted stronger IAS effects on present focus in both countries, on the health-related topic in the U.S. and on negativity in Taiwan. Air quality indicators amplified IAS effects, but the direction varied: stronger newspaper impact in Taiwan and stronger social media impact in the United States. We argue that cross-national variations are explained by cultural values and issue obtrusiveness: individualism empowered the effects of U.S. social media, while high issue relevance and poor air quality enhanced the influence of Taiwanese newspapers on social media.