# **C Sampling**

The city of Jakarta comprises 144 districts (‘Kelurahan’), which include the urban area of Jakarta proper as well as some agglomerations in the wider Jabodetabek metropolitan area. We restricted the sampling base for this study to the 112 districts in South, East and West urban Jakarta.<sup>9</sup> As a first step, 29 of the 112 districts were randomly selected to be included in the study.<sup>10</sup> Across the 29 selected districts, we first conducted a listing exercise of small retail shop owners that met the following three inclusion criteria: (1) the shop is at least 4 _m_<sup>2</sup> in size; (2) the shop offers at least two different product categories; and (3) the shop is at least 30 meters away from other shops in the listing. In addition, we excluded movable establishments, franchise businesses of larger retail chains, and shops located in densely populated marketplaces.

These listing criteria were chosen to ensure the sample would consist of business owners with an established store, who sold a variety of products, and where spillovers were minimized by design. Out of the 2,042 businesses listed through this method, we randomly selected 1,301 to be part of this study.

# **D Experimental Design and Timeline**

The 1,301 shops in the sample were randomly divided into a handbook treatment group ( _N_ = 1040) and a pure control group ( _N_ = 261), stratified by district, gender, shop size (below 6 _m_<sup>2</sup> , between 6 and 10 _m_<sup>2</sup> , or above 10 _m_<sup>2</sup> ), and a composite score of business practices (above and below the median). Among handbook recipients, we implemented two additional and orthogonal treatments: a screening of a documentary movie in which successful peers explained their own trajectory of growth adopting the best practices described in the handbook; and two individualized business assistance visits by a trained enumerator providing specific help on the adoption of business practices. Appendix Figure 2(a) maps the spatial distribution of our study sample across Jakarta and Appendix Figure 2(b) illustrates the spatial distribution in one sample district.

Overall, the study design consists of four experimental treatment arms of 260 firms each: handbook only ( _Handbook_ group), handbook and an invitation to the movie screening ( _Documentary_ group), handbook and two assistance visits ( _Assistance_ group), and all three interventions ( _All Three_ group).<sup>11</sup> The timing was as follows.<sup>12</sup> In January 2016 we sampled the 2042 businesses. In March and April 2016 we administered the baseline survey and registered the trial of the study at the American Economic Association’s Randomized-Controlled-Trial Registry website.<sup>13</sup> Interventions took place in October and November 2016 and were followed by a midline survey held in April and May 2017 and then an endline survey held in May 2018.

> 9We excluded all 32 villages of North Jakarta due to a MSE training program being run concurrently in that area by a local retail chain.

> 10We initially selected 30 districts, however, in one of these districts only five businesses were identified and they differed markedly from the remaining sample. Hence, they were dropped from the sample.

> 11Among the 1,040 handbooks, 520 had the economic returns to the adoption of each business practice described as gains and 520 had them described as losses. Since the focus of this paper is on social learning of local practices, we leave the analysis of eventual framing effects out of the scope of this paper and pool the two framing conditions. Appendix Figure 3 tabulates the various treatment arms of this study.

> 12See Appendix Figure 4 for a detailed timeline.

> 13https://www.socialscienceregistry.org/trials/1175.

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