For the most part, macroeconomics focuses on aggregate employment, ignoring distinctions among different categories of workers, but it sometimes considers broad categories, such as skilled and unskilled workers. Assume, for the sake of simplicity, that there are just these two categories, and that in general they cannot be substituted for each other.
(a) Draw demand and supply curves for skilled and unskilled workers, marking the initial equilibrium in each market.
(b) Assume now there is a technological change that increases the demand for skilled labor at each wage, while it shifts the demand curve for unskilled labor to the left. If wages do not adjust, can there be job vacancies of one type of labor at the same time there is unemployment of another type?