The selection of countries for the country studies is based on a stratified sample by countries' statistical capacity index and geographic regions. The statistical capacity index is based on the average capacity score for each of the six dimensions in the PARIS21 metabase. Within each strata, countries were selected at random and non-respondents were replaced with a random draw from their respective strata. In detail, the steps are the following:

1. The data used for the selection process is retrieved from the PARIS21 metabase.

2. In order to form a rating out of the PARIS21 metabase data, the data is decoded to binary, if needed, by formulating questions, e.g.: Was there a population census in the last 10 years? The binary data is then combined to the dimensions listed in the PARIS21 metabase using a weighted average. Together, the dimensions form the capacity index used for the selection.

3. Information on population, geographic region and income in form of gross national income (GNI) per capita are used to study the distribution of the capacity index. For twelve countries GNI information are not available. Hence, they are excluded from further analysis, reducing the number of countries from 136 to 124.

4. The sample design is based on the capacity index and the geographic region. The target number of countries covered in the country studies is 25. The sample count is proportional to the number of countries in a region. For example, having 17 African countries with a capacity index between 9 and 10 of a total of 124 countries equates to 3.4 (rounded 3) African countries with a capacity index between 9 and 10 in the target sample of 25 countries. Deviations might occur due to rounding.

5. Among the sample countries, the countries are selected randomly. Participation in the country studies has been offered to the respective NSOs while respecting their sovereignty. In case of non-response, countries are re-drawn. The final sample used for analysis consists of 29 countries.

6. The country selection for the in-depth country studies was conducted as described in 4. and 5. with a target sample of 7 countries and requiring participation in the cross-country study.