In addition, the hysteresis hypothesis says that the NAIRU does not stay the same over time—and can change due to economic policy. A persistently low unemployment rate makes it easier for those workers who are unemployed for "mismatch" reasons to move to where the jobs are and/or to attain the training necessary for the available vacancies (often by getting those jobs and receiving on-the-job training). On the other hand, high unemployment makes it more difficult for those workers to adjust, while hurting their morale, job-seeking skills, and the value of their work skills. Thus, some economists argue that British Prime Minister Margaret Thatcher's anti-inflation policies using persistently high unemployment led to higher mismatch or structural unemployment and a higher NAIRU.