All surveys in Morocco are based on a master sample based on the latest population census and all surveys use the same stratification structure. Based on the population census, the country is divided into sampling districts each including a fixed number of neighboring households. Each sampling district belongs to one exclusive stratified area. For urban areas, strata include the region, province, city size (large, medium and small) and type of housing (“lux”, “modern”, “old medina”, “new medina” and “clandestine”). For rural areas, the strata are regions and provinces. These are the stratas that apply to all surveys administered in Morocco and that are defined and updated with population censuses.

For all surveys, the first stage of sampling consists of creating the Primary Sampling Units (PSUs) by joining neighboring sampling districts so that each PSU contains an approximately equal number of households. Neighboring PSUs are then joined in groups of five to create the sampling areas. Based on sampling theory, 20% of PSUs are sufficient to survey a country so that only one in five PSUs within each sampling area is selected. This procedure represents the first stage of the sampling process, applies to all surveys administered in Morocco and results in the set of PSUs to be used for selecting the households to interview.

In Morocco, sampling methods can differ across surveys depending on whether sampling is two stages or three stages. The 2001 NCSE followed a two- stages sampling while the 2007 NLSS and the quarterly LFSs followed a three stages sampling process. For the 2001 NCSE and in the first stage, 1,250 PSUs (710 urban and 540 rural) of approximately 300 households each were extracted from the initial set of PSUs based on the 1994 population census. In the second stage, twelve households per PSUs were extracted with a systematic extraction method.<sup>7</sup> For the 2007 NLSS and the quarterly LFSs, 1,848 PSUs (1,124 urban and 724 rural) of approximately 600 household each were selected from the initial set of PSUs based on the 2004 population sample. In a second stage, PSUs were first subdivided into the Secondary Sample Units (SSUs) representing about 50 households each and six of the twelve SSUs were then extracted randomly from each PSUs. In a third stage, households to interview were selected with systematic extraction from each SSU.

# **5. Empirical model**

To build a model that is both flexible and parsimonious and in line with the samples stratification, we divide the data into urban and rural areas, and model each area separately. The labor markets, sector decomposition, returns to education, living conditions, the availability and use of infrastructure and the price of transport tend to be different between urban and rural areas which may be expected to lead to different models. In what follows, it can be seen for example that employment in agriculture matters in rural (both statistically and economically highly significant) but not in urban Morocco. The reverse holds

> 7 This method implies first defining the pace of extraction by dividing the number of households in each PSU by the number of households needed for the sample. Then a number is randomly extracted between 1 and the pace number. And finally household are extracted starting with the extracted number and using the pace number to identify each successive household.

12