Abstract We use a general equilibrium model to show that a decrease in workers’ bargaining power amplifies the contribution to the output gap of adjustments along the extensive versus intensive margin of labour utilization. Under standard assumptions on the disutility of labour, this mechanism reduces the cyclical movements of inflation relative to those of the output gap. Micro-level evidence, based on a survey of Italian firms, provides support to the relationship between bargaining power and adjustments along the extensive margin versus the intensive one, as well as to attenuated price response when firms adjust labour input mainly through the extensive margin. A Bayesian estimation using Italian aggregate data for the samples 1970–1990 and 1991–2014 confirms that the decline in workers’ bargaining power has weakened the inflation–output gap relationship.