According to the World Bank Group, certain factors are needed for PB to be adopted: "[…] strong mayoral support, a civil society willing and able to contribute to ongoing policy debates, a generally supportive political environment that insulates participatory budgeting from legislators' attacks, and financial resources to fund the projects selected by citizens." In addition, there are generally two approaches through which PB formulates: top-down versus bottom-up. The adoption of PB has been required by the federal government in nations such as Peru, while there are cases where local governments initiated PB independent from the national agenda such as Porto Alegre. With the bottom-up approach, NGO's and local organizations have played crucial roles in mobilizing and informing the community members.