Sampling Procedure
The Informal Surveys are conducted in selected urban centers, which are intended to coincide with the locations for the implementation of the main Enterprise Surveys. The overall number of interviews is pre-determined.
In Argentina, the urban centers identified were Buenos Aires and Resistencia in the province of Chaco. At the outset, the target sample for Buenos Aires was 240 interviews; the sample target for Chaco was 80 interviews.
Sampling in the Informal Surveys is conducted within clearly delineated sampling zones, which are geographically determined divisions within each urban center. Sampling zones are defined at the beginning of fieldwork, and are delineated according to the concentration and geographical dispersion of informal business activity.
The number of sampling areas, and the geographical area they contain, is determined with the goal that each sector will yield four effective interviews.
In Argentina, each sampling area was designed to contain a physical area, on average, of no less than the equivalent of ten city blocks. These sampling areas may
or may not correspond to the administrative districts of the urban center.
In Buenos Aires, for a total of 240 interviews, 60 sampling areas were initially identified (240/4 = 60 sampling areas). In Chaco, a total of 80 interviews yielded 20
sampling areas (80/4 = 20 sampling areas).
In order to provide information on diverse aspects of the informal economy, the sample is designed to have equal proportions of services and manufacturing (50:50). These sectors are defined by responses provided by each informal business to a question on the business's main activity included in the screener portion of the questionnaire.
As a general rule, services must constitute an ongoing business enterprise and so exclude the sale of manual labor Manufacturing activity in the informal sector includes business activity requiring inputs and/or intermediate goods. Thus, for example, the processing of coffee, sugar, oil, dried fruit, or other processed foods is considered manufacturing, while the simple selling of these goods falls under services. If an informal business conducts a mixture of these activities, the business is considered under the manufacturing stratum.
Each sampling zone was designed with the goal of obtaining two interviews in services and two interviews in manufacturing. In order to ensure a degree of geographical dispersion within each sampling zone, two starting points were identified.
Each starting point was designed to correspond to five city blocks, which were numbered sequentially. The first starting point was identified as Starting
Point A and the second as Starting Point B.
Proceeding from each starting point, interviewers were instructed to begin on block 1, defining the starting block and corner. Each interviewer was instructed to attempt to achieve two interviews from each starting point, ideally one interview in manufacturing and one in services.
Interviewers were instructed to proceed clockwise around block 1 from Starting Point A; if the target interviews were not achieved, interviewers proceeded to block 2, Starting Point A, and so forth until completing a circuit of block 5. After achieving two interviews from Starting Point A, interviewers were instructed to cease work in the blocks assigned to that given Starting Point and repeat the sameprocedure from Starting Point B, beginning with block 1.
Using local knowledge, within each block all houses and shops were checked for unregistered businesses, following the pre-fixed route described above, until the
allotted quota of interviews for each starting point was reached. Often interviewers used referrals by neighbors and locals in order to identify informal businesses. When a referral was obtained, the pre-determined route was followed until reaching the address of the referral. It should be noted that when referrals were obtained, interviewers were instructed to maintain the sampling procedure noted above; i.e., in the case that an interviewer encountered an informal business in the process of following a referral, an attempt was made to interview the former business first.
Each sampling zone, including its two starting points, were marked using Google maps, with the GPS coordinates of the starting points being systematically recorded.
Additionally, when obtaining a complete interview, the exact address of the informal business (or where the interview took place) was registered by the interviewer. Once in the office, this address was searched in Google maps, and its GPS coordinates were registered in a fieldwork report.
If no address was immediately available, using local knowledge, the GPS coordinates were determined using imaging via Google maps. In order to preserve confidentiality, the exact coordinates of businesses are not published.
Due to issues of non-response, in the process of fieldwork, the implementing contractor was unable to obtain the targeted four interviews in each of the originally delineated sectors.
As a result, replacement sectors were delineated, ex post. Additionally, the implementing contractor noted that in various interviews there were notable shortfalls in response rates to certain questions. For these reasons, additional interviews were authorized. These were distributed according to the discretion of the implementing contractor in Argentina, with authorization from the World Bank.
Continuing with the sample target of four interviews per sector, as a result of the replacement procedure, more than the original target of interviews per urban center were realized, 100 in Chaco (target 80) and 284 in Buenos Aires (target 240).
In sum, there were 64 zones (60 original, 4 replacement) in Buenos Aires and 27 zones in Chaco (20 original, 7 replacement).
Complete information regarding the sampling methodology as well as maps of starting points can be found in "Description of Argentina Informal Survey Implementation" and "Mapping of starting points for sampling in Argentina Informal Survey 2010" in "Technical Documents" folder.