components from broader state incentive programs, but their implementation is very much tailored to local needs. The wide variation in current pay-for-performance programs suggests that successful design and implementation depends in large part on the local context. Diversification can help make a program politically feasible by satisfying multiple stakeholders, and can also reward teachers for undertaking a wide range of important behaviors, lessening incentives to focus on narrow (but rewarded) tasks. On the other hand, too many overlapping programs can obscure the educational goals of the district. Johnson and Papay note that, for the most part, too many districts have simply appended performance pay components to their current pay system. They suggest that performance-based pay should instead be part of a well-conceived human capital strategy for developing teachers through all stages of their career. This volume's second study, "Pay and Career Development: A Proposal for a New Generation of Teachers," is an example of such a strategy. In this section, Johnson and Papay propose to replace the single salary scale with a career-oriented compensation system that is aligned with school districts' strategies for developing human capital. This system, dubbed the "Tiered Pay-and-Career Structure," is designed to attract strong candidates to teaching, to support them in developing instructional skills throughout their career, and to provide substantially higher pay to those who perform well and assume broader responsibility for improving instruction beyond their classroom. This new proposal is motivated by the needs of students and schools today, particularly those in low-income communities.