For information related to survey data, we focused on schemata based on the **Data Documentation Initiative (DDI)** , an international standard for documenting survey data (DDI, 2021), in particular the fields used in the Harvard Dataverse and the International Household Survey Network (IHSN) template of the World Bank Microdata Catalog. The **Harvard Dataverse** is an accredited, cross-disciplinary data repository that enables any researcher or institution to publish and archive data and code. J-PAL and IPA maintain a Dataverse data collection called the “Datahub for Field Experiments in Economics and Public Policy” that currently hosts over 200 RCT datasets. The repository builds on a suite of tools for the publication of scholarly data (King, 2007), and its metadata schema is mapped to the DDI Codebook. The schema is organized in blocks that can be used to customize the metadata documentation in individual data collections (Harvard Dataverse, 2021). We considered all blocks used by the J-PAL/IPA Datahub.

The **World Bank Microdata Library** hosts survey and other data from multiple institutions, including the World Bank’s own research departments, which publish their data under the World Bank’s Open Data Policy. It aggregates multiple named collections, including those of the Development Economics Research Group (DECRG), the Development Impact Evaluation Unit (DIME), and the Strategic Impact Evaluation Fund (SIEF),<sup>6</sup> and all metadata can be accessed through an Automated Programming Interface (API) (The World Bank, 2022). The World Bank’s IHSN microdata template has four sections compatible with DDI – Document Description, Study Description, Datasets, and Variables Groups – and an External Resources section compatible with the Dublin Core metadata standard (IHSN, 2022). We considered all of these for the schema and adopted many usage recommendations from Dupriez et al. (2021).

Most existing data catalogs do not cover fields related specifically to the design of RCTs. For these, we turned to two important trial registries. The **AEA RCT Registry** of the American Economic Association is likely the most complete record of past and ongoing RCTs in economics, including unpublished studies (AEA RCT Registry, 2022). The registry metadata contains information specific to RCTs that is not typically included in survey schemata, such as the intervention, randomization method, outcome measures, or the reviewing IRB, although these contents are mostly stored in free text fields and there is no cross walk with DDI or other metadata standards. The US National Library of Medicine and the National Institutes of Health maintain the trial registry and results database **ClinicalTrials.gov** for clinical trials in the United States (McCray and Ide, 2000). All clinical studies of drugs and devices controlled by the Food and Drug Administration (FDA) must be registered here. The registry has detailed metadata field definitions and maintains an API feed (ClinicalTrials.gov, 2022). Many repositories draw from or link to this registry (e.g. Vivli, 2022; ISRCTN, 2022). The fields on interventions, study arms, and outcome measures provided a

> 6Impact evaluation often means RCT in this context but can also mean other rigorous analysis methods aimed at estimating causal impacts.

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