America's capacity utilisation, for example, hit historically high levels earlier this year, and its jobless rate (5.6% in August) has fallen below most estimates of the natural rate of unemployment—the rate below which inflation has taken off in the past.
I don't understand the sentence after the dash mark. First, does the rate refer to jobless rate or the natural rate of unemployment? Second, I don't understand the meaning of the last sentence neither in the context of jobless rate nor the natural rate of unemployment. Is the author using the subjunctive mood? It would be nice if someone could explain or rewrite the last sentence for me.