Deciding "who gets what, when, and how" are perhaps the most important decisions any government has to make. So it should not be surprising that around the world, government officials responsible for public budgeting are facing demands to make their patterns of spending more transparent and their processes more participatory. These demands are coming from their own citizens as well as from other government officials, economic actors, and increasingly from international sources—all of whom are looking for more open and inclusive processes for establishing how valuable public resources are spent. Rigorous analysis of public budget transparency and participation has been thin at best. Open Budgets is a major step forward in our understanding of powerful changes. What are the characteristics, causes, and consequences of the shift toward greater transparency, participation, and accountability? Where is it happening, under what conditions, and what does the future hold for this trend? Sanjeev Khagram, Archon Fung, Paolo de Renzio, and their contributors explicate political economy factors that have brought about greater transparency and participation in budget settings across Asia, Africa, and Latin America. They dissect the strategies, policies, and institutions through which improvements can occur and produce change in policy and institutional outcomes, considering the potentially broad societal impacts over the long term. This international movement—aided by the Open Government Partnership recently launched by President Obama and other heads of state at the UN General Assembly—is picking up steam, as seen in the Arab Spring. Open Budgets clarifies what these dramatic trends and patterns mean and how they are playing out worldwide.