It's a purely procedural standard. To oversimplify a bit: if the employer meets with the union's designees (e.g. workers elected by their peers, a lawyer hired

It's a purely procedural standard. To oversimplify a bit: if the employer meets with the union's designees (e.g. workers elected by their peers, a lawyer hired by the union), exchanges proposals verbally or in writing, and goes through the motions until reaching a so-called "valid impasse", they have made good on their duty to bargain. They could propose nothing but cuts to wages and conditions, and indeed this happens often if workers don't have a credible strike threat. See: https://www.nlrb.gov/about-nlrb/rights-we-protect/the-law/bargaining-in-good-faith-with-employees-union-representative https://www.nlrb.gov/about-nlrb/rights-we-protect/the-law/ba... The model you have in mind - make concessions or have more general terms impose by a regulatory body - does exist in other countries, where parties have to go to a sectoral body, interest arbitration, etc. when impasse is reached. Interest arbitration was a proposed reform in the (now dead) PRO Act that the Biden administration favored early on.