"Empirical studies have shown that union members are more likely to participate in collective actions than nonunion members. However, we still know little about the mechanisms that explain why this occurs. In this article, we aim to fill this gap in the literature. Using data from the World Values Survey for Argentina and Chile (2006–2018), we employed the Karlson–Holm–Breen mediation analysis to analyze the degree to which the relationship between union membership and participation in demonstrations and strikes is explained by union members' higher levels of politicization and stronger left-wing orientation, as hypothesized in previous studies. We found that in the two countries these two mediators explain more than 30% of the relationship between union membership and participation in demonstrations. We also found that these two mediators explain around 20% of the relationship between union membership and strike participation in Argentina, and nearly 40% of such relationship in Chile. At the end of the article, we offer some explanations for these findings and show how they contribute to the literature on trade unions, class politics, and industrial relations."

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