Literature about unemployment

In recent years a large literature has developed which explores the idea that persistence in
unemployment might be explained by the tendency for actual unemployment to cause an upward movement in equilibrium unemployment. So what you need in your answer is to explain hysteresis i.e. how extended period of cyclical unemployment can result in higher NRU. The term hysteresis comes from a Greek verb meaning ‘that which comes after’ and therefore refers to effects which persist after the initial impulse which gave rise to those effects is removed. Hence another theory that has also been used to explain hysteresis is the insider/outsider model of decision making about employment. Insiders such as the unionized workers ratchet up wage rates beyond where it is profitable to hire the unemployed. Outsiders who are unemployed don't get to be part of the negotiation process.