"Are workers equal in front of employers' concentration? We show, using instrumental variable estimations for France between 2000 and 2019, that employers' concentration has a negative heterogenous effect on wage, with the lowest earners being the most vulnerable. This increased wage inequality could reflect some efficiency gains if concentration allows employers to impose a more demanding selection process, improving sorting i.e. workers selection, thus generating both inequality and higher productivity. We find, exploring within-firm and between-firm inequality, that it is not the case. Employers' concentration instead generates wage inequality by undercutting relatively more the bargaining power of the lowest earners."

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