Participatory budgeting is a democratic practice that was first implemented in Latin America in the late 80’, traveled the world and it’s now been instituted in 1500 cities worldwide. Several scholars highlights the positive impact of participatory budgeting for the quality of life in cities and for democratic legitimacy and in particular his potentiality to include vulnerable communities. On the other side, scientific studies also reveals limits of this democratic innovation, due for instance to the intensity of worldwide diffusion, and put the lights on the riks of transforming a democratic process into a sterile set of procedures.
In the European Union Context, a relevant example is the Paris case, the bigger in the EU, and in Italy this experiment is been conducted in some middle size and small size cities, mainly through the Bipart platform.
Participatory budgeting in New York City
In the USA and Canadian context, participatory budgeting in recently been implemented, in Toronto, Chicago and New York City. The PB in New York was first implemented as a pilot project from 2011 to 2012 and was initiated by four members of the New City Council, three Democrats and one Republican: Brad Lander, Melissa Mark-Viverito, Eric Ulrich, and Jumaane D. Williams. They’ve chosen to allocate for Participatory Budgeting the discretionary funds (capital money) of their budget. The four council members decided to put a part of their budget directly in the hands of their constituency, for an amount of at least 1 million dollars.
After the pilot project was realized, Participatory budgeting in New York City expanded dramatically and it’s been adopted by 28 council members. In 2016, 67,000 New Yorkers voted to allocate $38 million for locally-developed capital projects across 28 Council Districts in New York City. Currently, the sixth cycle of PB is ongoing.
There are several kind of projects that can be proposed: improvements to schools, parks, libraries, public housing, and other public or community spaces. The process is designed to meet needs of communities and to ensure involvement of all the local actors. The first phase of the process consist in public discussions, the Neighborhood Assemblies, realized in each district were people can learn more about the process and discuss the needs of the neighborhood. At the end of this phase, volunteers from the community, the Budget delegates, are selected and the first ideas are collected also though the Idea Collection Map. Budget Delegates, work on the ideas in order to turn them into real proposals for a ballot, with input also from city agencies, that ensure feasibility and coordination of proposals. These proposals will be up for a community-wide vote. The Council Members then submit the projects with the most votes to City Council for inclusion in the final city budget. Community members evaluate the process, and oversee the implementation of projects.
More information about the phases of the project are available here: http://labs.council.nyc/pb/ and here: http://ideas.pbnyc.org/page/about-. To see research on the impact of Participatory Budgeting, you can have a look at the annual research reports published by the Community Development Project of the Urban Justice Center:
The participatory budgeting process in NYC is supported technically by the Participatory Budgeting Project, a non profit organization that create and support participatory budgeting processes in several context in the United States of America and in Canada. On the basis of their large experience, both theoretical and on the ground, they developed Guidelines and Tools to implement Participatory Budgeting in cities: http://www.participatorybudgeting.org/resources/sample-materials/ .
The issue is been studied also from an institutional standpoint. The World bank, European Union and the United Nations have worked intensely on this issue, given his relevance for democracy and his great diffusions, and developed opinions and toolkit.
 Wampler, B. “A Guide to Participatory Budgeting” In. Participatory Budgeting edited by Shan, A. Washington DC, The World Bank (2007); Smith, G. Democratic Innovations. Cambridge, CUP (2009); G. Baiocchi, P. Heller, and M. K. Silva Bootstrapping Democracy: Transforming Local Governance and Civil Society in Brazil, Standford University Press (2011).
 E. Ganuza and G. Baiocchi, The Power of Ambiguity: How Participatory Budgeting Travels the Globe Journal of Public Deliberation Volume 8 Issue 2 Article 8 (2012).
 See generally H.R. Gilman, Democracy reinvented, Brookings, (2016).