This question is important for anyone committed to the goal of maximum employment, because it implicitly asks whether the best we can hope for, even in a healthy economy, is an unemployment rate significantly higher than what has been achieved in the past. For the Federal Reserve, the answer to this question has important implications for monetary policy.
If the current, elevated rate of unemployment is largely cyclical, then the straightforward solution is to take action to raise aggregate demand. If unemployment is instead substantially structural, some worry that attempts to raise aggregate demand will have little effect on unemployment and serve only to stoke inflation.