"International comparative research has found that strike incidence is higher where two or more unions bargain with an employer ("multi-unionism"), as is common in most European countries, than where only one union does, all else equal. Two proposed explanations for this relationship, both invoking inter-union rivalry as the main dynamic, are that under multi-unionism, unions (a) make propagandistic use of strikes to attract members, or (b) compete with each other by bidding up bargaining demands. To date, the evidence bearing on these hypotheses has been equivocal because, the author argues, researchers have focused on activity at the national level rather than at the lower levels that are more commonly the nexus for strike formation. The author performs empirical tests using industry-sector-level data for seven European countries for the years 1990-2006, and finds evidence clearly favoring the competitive bargaining hypothesis over the propaganda hypothesis."

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