Brian Jacob examines challenges faced by urban districts in staffing their schools with effective teachers. He emphasizes that the problem is far from uniform. Teacher shortages are more severe in certain subjects and grades than others, and differ dramatically from one school to another. The Chicago public schools, for example, regularly receive roughly ten applicants for each teaching position. But many applicants are interested in specific schools, and district officials struggle to find candidates for highly impoverished schools. Urban districts' difficulty in attracting and hiring teachers, says Jacob, means that urban teachers are less highly qualified than their suburban counterparts with respect to characteristics such as experience, educational background, and teaching certification. But they may not thus be less effective teachers. Jacob cites recent studies that have found that many teacher characteristics bear surprisingly little relationship to student outcomes. Policies to enhance teacher quality must thus be evaluated in terms of their effect on student achievement, not in terms of conventional teacher characteristics. Jacob then discusses how supply and demand contribute to urban teacher shortages. Supply factors involve wages, working conditions, and geographic proximity between teacher candidates and schools. Urban districts have tried various strategies to increase the supply of teacher candidates (including salary increases and targeted bonuses) and to improve retention rates (including mentoring programs). But there is little rigorous research evidence on the effectiveness of these strategies. Demand also has a role in urban teacher shortages. Administrators in urban schools may not recognize or value high-quality teachers. Human resource departments restrict district officials from making job offers until late in the hiring season, after many candidates have accepted positions elsewhere. Jacob argues that urban districts must improve hiring practices and also reevaluate policies for teacher tenure so that ineffective teachers can be dismissed.