Rwanda - Micro-Enterprise Survey 2011

The sample was selected using stratified random sampling technique. Two levels of stratification were used: firm sector and geographic region.

Industry stratification was designed in the way that follows: the universe was stratified into one manufacturing industry and one service industry. The sample design for the micro-survey targeted 170 establishments: 18 in manufacturing and 152 in services.

Regional stratification was defined in two regions: Butare and Kigali City.

The micro sample consists of firms with 1 to 4 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, casua and part-time employment is not a common practice, except in the sectors of construction and agriculture.

The sample frame was produced by Rwanda Revenue Authority. The enumerated bussinesses with less than five employees were used as sample frame for the Rwanda Micro-Survey with the aim of obtaining interviews at 170 establishments.

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 noneligibility, repetition, non-existent units, etc. In addition, the sample frame contains no telephone or 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 15% (66 out of 433) for micro firms.


Survey non-response must be differentiated from item non-response. The former refers to refusals to participate in the survey altogether whereas the latter refers to the refusals to answer some specific questions. Enterprise Surveys suffer from both problems and different strategies were used to address these issues.

Item non-response was addressed by two strategies:
a- For sensitive questions that may generate negative reactions from the respondent, such as corruption or tax evasion, enumerators were instructed to collect "Refusal to respond" (-8) as a different option from "Don't know" (-9).
b- Establishments with incomplete information were re-contacted in order to complete this information, whenever necessary.

Survey non-response was addressed by maximizing efforts to contact establishments that were initially selected for interview. Attempts were made to contact the establishment for interview at different times, days of the week before a replacement establishment (with similar strata characteristics) was suggested for interview. Survey non-response did occur but substitutions were made in order to potentially achieve strata-specific goals.

The number of contacted micro establishments per realized interview was 0.34. This number is the result of two factors: explicit refusals to participate in the survey, as reflected by the rate of rejection (which includes rejections of the screener and the main survey) and the quality of the sample frame, as represented by the presence of ineligible units. The number of rejections per contact was 0.18.

Complete information regarding the sampling methodology, sample frame, weights, response rates, and implementation can be found in "Description of Rwanda ES 2011 Implementation" in Technical Documents.


For some units it was impossible to determine eligibility because the contact was not successfully completed. Consequently, different assumptions as to their eligibility result in different universe cells' adjustments and in different sampling weights. Three sets of assumptions were considered:

a- Strict assumption: eligible establishments are only those for which it was possible to directly determine eligibility.

b- Median assumption: eligible establishments are those for which it was possible to directly determine eligibility and those that rejected the screener questionnaire or an answering machine or fax was the only response. Median weights are used for computing indicators on the www.enterprisesurveys.org website.

c- Weak assumption: in addition to the establishments included in points a and b, all establishments for which it was not possible to finalize a contact are assumed eligible. This includes establishments with dead or out of service phone lines, establishments that never answered the phone, and establishments with incorrect addresses for which it was impossible to find a new address. Note that under the weak assumption only observed non-eligible units are excluded from universe projections.