In Netherland, unions negotiate with employers, generally with the government also at the table, to agree on workplace conditions and pay scales that apply to the whole industry, and not just the union members. The employer gains nothing by hiring a non-union member, and besides, a non-union member can always join the union if they want to.
The same system is used in most of Scandinavia, the union-government-employer tripod where the government acts as a facilitator and the union and employers negotiate a collective agreement.
I read a study on international power polarities, and they noted that truly independent tripolar was among the most stable configurations from a game theory perspective.
Broadly summarizing, the potential for the remaining tie-breaker to defect to either side tends to keep participants honest, even if they're bitterly opposed.
I think a lot of people worry about these pay scales being limiting. In the US, they tend to end up being based on years of service or credentials, rather than about productivity or quality.
In Netherland they tend to be based on your function, and within that function, how well you perform it. Companies tend to want the best people in the most important functions. If you think you're performing the function of a higher paid role, that's a good argument to ask for a raise. Or a promotion.
It works surprisingly well. A decade or two ago this was widely praised as the "polder" system: instead of going on strike and firing people all the time, you talk it out and find a solution that works for everybody. Everybody involved has an interest in a good solution.
