Matt Ryan's landmark comparative review of participatory budgeting, or collective decisions on spending and taxation, reveals the factors behind its success in achieving democratic engagement. The culmination of ten years of research into participation, this is a systematic analysis of how, when and why citizens gain control over these important decisions. Comparing global examples of both positive change and notable failure, the book provides persuasive evidence and guidance for future public involvement in taxation and spending. For advocates and participants of democratic reform and those with interests across political science, this is an essential guide to one of the most significant democratic innovations of our times.