Why is a cashier at Carrefour more expensive than at Albert Heijn?

After Colruyt and the trade unions, the CEO of Carrefour in Belgium is now also calling for a reform of wages and working conditions in the sector. But what exactly is the difference when you work for Colruyt, Carrefour, Delhaize or another supermarket? And why does someone behind the cash register earn more at one than at the other?

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