Enterprise Survey 2010

The sample for The Democratic Republic of the Congo (DRC) was selected using stratified random sampling. Three levels of stratification were used in this country: firm sector, firm size, and geographic region.

For industry stratification, universe was divided into one manufacturing industry, one service industry (retail), and one residual sector. The manufacturing industry, service industry, and residual sectors had a target of 120 interviews each.

Size stratification was defined following the standardized definition for the Enterprise Surveys: small (5 to 19 employees), medium (20 to 99 employees), and large (more than 99 employees). For stratification purposes, the number of employees was defined on the basis of reported permanent full-time workers. This seems to be an appropriate definition of the labor force since seasonal/casual/part-time employment is not a common practice, except in the sectors of construction and agriculture.

Regional stratification was defined in four regions (city and the surrounding business area): Kinshasa, Kisangani, Lubumbashi, and Matadi.

For The Democratic Republic of the Congo, three sample frames were used.

The first was supplied by the World Bank and consists of enterprises interviewed in DRC 2006. The World Bank required that attempts should be made to re-interview establishments responding to the DRC 2006 survey where they were within the selected geographical regions and met eligibility criteria. Due to the fact that the previous round of surveys seemed to have utilized different stratification criteria (or no stratification at all) and due to the prevalence of small firm in the 2006 sample the following convention was used. To avoid oversampling smaller firms and to limit the presence of Panel firms to a maximum of 50% of the achieved interviews, a decision was made to restrict the number of issued firms with less than 20 employees. That sample is referred to as the Panel.

The second and third sample frames were files produced by Fédération Entreprises du Congo (FEC) and Confédération des Petites et Moyennes Entreprises du Congo (COPEMECO). A copy of that frames was sent to the TNS statistical team in London to select the establishments for interview.

During fieldwork it has been realized that the original classification did not respect the reality of the firms; this was true especially for "Grands cotisants" in Lubumbashi that resulted to be mainly Small/Medium firms. Thus appropriate adjustments to the target sample was made. Furthermore, to avoid oversampling of small firms in the panel sample (around 77% of 2006 sample) a decision was made to only attempt re-interviewing around half of the small firms sample.

The quality of the frame was assessed at the onset of the project through visits to a random subset of firms and local contractor knowledge. The sample frame was not immune from the typical problems found in establishment surveys: positive rates of non-eligibility, repetition, non-existent units, etc. In addition, the sample frame contains no telephone/fax numbers so the local contractor had to screen the contacts by visiting them. Due to response rate and ineligibility issues, additional sample had to be extracted by the World Bank in order to obtain enough eligible contacts and meet the sample targets.

Given the impact that non-eligible units included in the sample universe may have on the results, adjustments may be needed when computing the appropriate weights for individual observations. The percentage of confirmed non-eligible units as a proportion of the total number of sampled establishments contacted for the survey was 6.87% (43 out of 626 establishments).