Philanthropists and governments have long used prizes to drive innovation and engagement to produce societal benefit, but the use of this powerful instrument is undergoing a renaissance. Philanthropic prizes are growing in number and size, are appearing in new forms, and are being applied to a wider range of societal objectives by a wider range of sponsors than ever before. Not all of the growth has been positive, however, as the many overlapping prizes and growing clutter of the sector attests. In response, current and potential participants are asking when they should use prizes, and how they can develop and deliver effective ones. This report addresses these questions by drawing on academic literature, interviews with analysts and practitioners, surveys of prize sponsors and competitors, databases of small and large awards, and case studies of twelve effective prizes to produce lessons from a range of sectors, goals, and prize types. It aims to help improve current prizes and stimulate effective future use by developing a number of simple frameworks and compiling useful lessons for sponsors. While targeting the philanthropic sponsor, we believe these perspectives will also be helpful to governments and corporations considering prizes. Our research found that prizes are a unique and powerful tool that should be in the basic toolkit of many of today's philanthropists. Their recent renaissance is largely due to a new appreciation for the multiple ways in which they can produce change: not only by identifying new levels of excellence and by encouraging specific innovations, but also by changing wider perceptions, improving the performance of communities of problem-solvers, building the skills of individuals, and mobilizing new talent or capital. These change drivers give prize sponsors compelling opportunities to use the open, competitive, and media-friendly attributes of prizes to stimulate attention and drive innovation in a highly leveraged and result-focused way. Recent prize growth is reinforced by powerful external trends such as the arrival of new philanthropic wealth, different attitudes to shifting risk, interest in open source approaches, and an increasingly networked, media-driven and technology-intensive world. We believe that the outlook for prizes is particularly strong because of the increased interest of philanthropists and the emergence of an industry of prize facilitators that is driving improvements in prize economics and improved practices for managing execution challenges and risks.