Denmark also has that system, but part of it is law in addition to tradition. It's essentially impossible to be a large employer and refuse to negotiate with a

Denmark also has that system, but part of it is law in addition to tradition. It's essentially impossible to be a large employer and refuse to negotiate with a union— all large workplaces have labor agreements in place. So there isn't the whole American system of "unionization drives" where unions try to "unionize" a workplace and companies try to keep it "non-unionized"; working conditions are negotiated between the employer and a union by default, except in some small shops. In cases where no one union represents the employees (at my workplace, employees belong to several different unions, and some belong to none), one union is appointed to be the main negotiator. The union system is also much more highly coordinated, though part of that is indeed traditional rather than in law. Rather than every union having to negotiate its own conditions, some conditions are agreed at the central level, in framework agreements reached between the Confederation of Danish Employers (DA) and the Danish Confederation of Trade Unions (LO). The minimum wage is one of those: effectively all Danish workplaces have a minimum wage of 109 DKK/hr, the amount agreed to in the last framework negotiation.