# Annex Survey Methodology

In 2011 the World Bank – with funding from the Bill & Melinda Gates Foundation – launched the Global Findex database, the world’s most comprehensive data set on how adults save, borrow, make payments, and manage risk. Drawing on survey data collected in collaboration with Gallup, Inc., the Global Findex database covers almost 150,000 people in 144 economies—representing more than 97 percent of the world’s population.<sup>2</sup> The initial survey round was followed by a second one in 2014 and by a third in 2017.

The 2017 survey was carried out over the 2017 calendar year by Gallup, Inc., as part of its Gallup World Poll, which since 2005 has conducted annual surveys of approximately 1,000 people in each of more than 160 economies, in more than 150 languages, using randomly selected, nationally representative samples. The target population is the entire civilian, noninstitutionalized population age 15 and older.

## _Interview Procedure_

Surveys are conducted face to face in economies where telephone coverage represents less than 80 percent of the population or where doing so is the customary methodology. In most economies, fieldwork is completed in two to four weeks.

In economies where face‐to‐face surveys are conducted, the first stage of sampling is the identification of the primary sampling units. These units are stratified by population size, geography, or both; clustering is achieved through one or more stages of sampling. Where population information is available, sample selection is based on probabilities proportional to population size; otherwise, simple random sampling is used.

Random route procedures are used to select sampled households. Unless an outright refusal occurs, interviewers make up to three attempts to survey the sampled household. To increase the probability of contact and completion, attempts are made at different times of the day and, where possible, on different days. If an interview cannot be obtained at the initial sampled household, a simple substitution method is used.

Respondents are randomly selected within the selected households. Each eligible household member is listed, and the handheld survey device randomly selects the household member to be interviewed. For paper surveys, the Kish grid method is used to select the respondent.<sup>3</sup> In economies where cultural restrictions dictate gender matching, respondents are randomly selected from among all eligible adults of the interviewer’s gender.

In economies where telephone interviewing is employed, random digit dialing or a nationally representative list of phone numbers is used. In most economies where cell phone penetration is high, a dual sampling frame is used. Random selection of respondents is achieved by using either the latest

> 2 For a list of the economies included, see table A.1 in the 2017 Global Findex Database, “Measuring Financial Inclusion and the Fintech Revolution” (Demirgüç‐Kunt and others 2018). It shows the data collection period, the number of interviews, the approximate design effect, and the margin of error for each economy as well as sampling details, where relevant.

> 3 The Kish grid is a table of numbers used to select an interviewee. First, the interviewer lists the name, gender, and age of all permanent household members age 15 and older, whether or not they are present, in order by age. Second, the interviewer finds the column number of the Kish grid that corresponds to the last digit of the questionnaire and the row number for the number of eligible household members. The number in the cell where the column and row intersect is the person selected for the interview.

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