When have good-faith negotiations reached an impasse?

The case of Carey Salt Co. v. NLRB dealt with a technical labor law question as to when negotiations between management and a union had reached an impasse.  No. 12-60757 (Nov. 21, 2013).  The general framework it uses, though, is of broad interest in court-ordered mediation, contractual dispute resolution clauses, and other situations where a party’s good faith in negotiation can come into question.  The opinion is centered on the factors identified in Taft Broadcasting Co., 163 N.L.R.B. 475, 478 (1967): “(1) the parties’ bargaining history; (2) the parties’ good faith; (3) the duration of negotiations; (4) the importance of issues generating disagreement; and (5) the parties’ contemporaneous understanding of the state of negotiations.”  That NLRB case also noted the general importance of overall “good faith.”