The remainder of this section summarizes existing evidence on CDD’s impacts on inclusion, resilience, cohesion, and process legitimacy outcomes. The purpose of this review is to motivate a forward-looking learning agenda by highlighting the main unanswered questions related to CDD. The review draws on and extends other recent reviews of the CDD literature, mainly Wong and Guggenheim (2018) and Winkler and Linneman (2022). Our review contributes to this past work by summarizing CDD’s impacts on social sustainability outcomes as a way of illustrating how CDD projects can be a tool to address multiple complex and overlapping development challenges. We also contribute a focus on identifying what remains unknown about CDD’s impacts across core outcomes so that we can recommend approaches to answer these unknowns (Section 4). Our starting point for the review is the same sample used in Winkler and Linneman (2022), which focused on 104 publicly available impact evaluations, academic studies, project audit reports, monitoring reports, and internal evaluations of World Bank-financed CDD projects.<sup>19</sup> We also include prominent studies of non-World Bank-financed projects if they are particularly relevant to the CDD literature or to the identified gaps in the literature. As noted above, CDD is used to describe many different types of projects.<sup>20</sup> We apply the above scope conditions to ensure some consistency in the projects we are reviewing and to focus on the types of projects that are often requested and financed at scale by governments.

# 3.1 Inclusion

## _Infrastructure and services_

One of the most consistent findings on CDD is that block grants to communities can improve access to, and the quality of, basic infrastructure and services. A meta-analysis of rigorous CDD evaluations, including World Bank-financed projects in Afghanistan and Sierra Leone, found that CDD projects can contribute to a robust and statistically significant<sup>21</sup> increase in the bundle of local public goods including access to clean water, hours of electricity, education and health outcomes, and infrastructure quality of education and health facilities (Casey 2018). A randomized control trial (RCT) of Afghanistan’s _National Solidarity Program (NSP)_ found that women were especially likely to benefit from increased access to education, health care, and counseling services, and that the program significantly increased access to clean, protected water sources and increased usage of electricity (Beath et al. 2013). In Sierra Leone, the _GoBifo_ project led to significant improvements in local public infrastructure, including more functional latrines, community centers, agricultural drying floors, and foot paths (Casey, Glennerster, and Miguel 2013). A follow-up study conducted 11 years after the start of _GoBifo_ found that these positive impacts on functional public infrastructure persisted over the long run (Casey et al. 2023). A separate study found that _GoBifo_ was less effective at providing local public goods in larger communities (Anderson and Magruder 2017). In the Lao People’s Democratic Republic, the _Poverty Reduction Fund II (PRFII)_ project also increased access to protected water sources, improved community members’ perceptions of school quality, and decreased travel times to neighboring villages (World Bank 2016b). In the Solomon Islands,

> 19 Here, CDD projects are defined as those that include a direct financial resource transfer to administratively defined communities that the community can use for productive investments (i.e., small-scale infrastructure, revolving loans).

> 20 For a more detailed overview of the different types of CDD projects, see Wong and Guggenheim (2018) and Mansuri and Rao (2012).

> 21 The treatment effect for all CDD projects in the meta-analysis was 0.119 standard deviation units with a standard error of 0.025.

11