It's never a good idea. It's not really a power imbalance that matters, but rather that the powerful will consider an arbiter's past decisions in deciding whet

It's never a good idea. It's not really a power imbalance that matters, but rather that the powerful will consider an arbiter's past decisions in deciding whether to accept them. Thus an arbiter who wants to keep on being an arbiter will tilt things considerably towards the powerful and an arbiter between two powerful entities will split their decisions about in the middle. Give a union binding arbitration and they can simply double their demands and end up with basically whatever they really asked for in the long run.