Quote from blackjack007:
you're forgetting there's a floor in the UE rate.
the minimum unemployment rate is around 3%. it never goes below this, even if GDP is growing 10%. the reason is, there's always some people who are between jobs. maybe their company went bankrupt and it takes 1 week to find a new job. or perhaps someone got fed up and quit before even finding a new job, but they're confident they can find something soon. or maybe someone was an incompetent employee and was fired.
you are referring to friction. the various types of friction are mostly represented in my groupings.