Structural unemployment may also be encouraged to rise by persistent cyclical unemployment: if an economy suffers from long-lasting low aggregate demand, it means that many of the unemployed become disheartened, while their skills (including job-searching skills) become "rusty" and obsolete. Problems with debt may lead to homelessness and a fall into the vicious circle of poverty. This means that they may not fit the job vacancies that are created when the economy recovers. The implication is that sustained high demand may lower structural unemployment. This theory of persistence in structural unemployment has been referred to as an example of path dependence or "hysteresis."