Experimental Design Details
The units of analysis in this RCT are census tracts (secciones censales) in Spain. As a first step to select which census tracts would participate in the experiment, EAPN-ES chose 510 census tracts with high shares of low-income population and that had the appropriate facilities and network of collaborators for the intervention to operate. To verify the first criterion, the partner used information from the Spanish National Statistics Institute regarding the percentage of households with income below 40% of the median income residing in each census tract (40% of the median household median income corresponds to approximately to 535 euros a month in 2020). To verify the second criterion, the partner consulted through their network of NGOs if they had a local NGO or organization that could lend appropriate facilities to conduct the intervention. In particular, some indoor private office space to help with the applications was necessary. Note that, while the presence of local organizations was important, the treatment was provided in a centralized manner by the partner organization EAPN-ES. We provide more details on this below.
Those facilities were referred as “contact point”, and they are typically within the census tract of study or near them. A contact point could be, for example, a social center, a day center, a soup kitchen, an association, a reception center, or a homeless shelter. In this project, each census tract selected is called a “node” and each contact point is the “point”. As will be explained in the description of the interventions, the node becomes the relevant unit for the outreach campaign, as it is where posters will be placed, and flyers distributed. However, the counseling and support for applying to the benefit was conducted at the point. In the case of the social media intervention, the treatment is done at the zip code level corresponding to the node.
The research team in collaboration with the Ministry did the second step to select 400 nodes out of the initial 510 nodes proposed by the partner. We visualized the nodes and points in a map and eliminated from the initial proposal those that were in proximity in order to minimize the risk of contamination. Finally, EAPN-ES further eliminated some additional nodes whose distribution across the regions was complicated for logistical reasons. The final sample of 400 nodes is at least 300 meters of distance from any other node and they do not share the same postal code as any other node.