Enquete Nationale sur la Consommation et les Dépense des Ménages 2000-2001

Sampling
The ENCDM 2000/01 sampling plan comes within the framework of the master-sample, put in 1983 and updated in 1994, to meet sampling needs of post-poll tax surveys.

The main features of this drilling plan are summed up as follows:

Master-sample:
The 'master-sample' expression refers to a set of geographic zones or « primary units » (UP), within which samples to carry out the various surveys with households are chosen.

To elaborate the master-sample, a set of 2 or 3 adjacent survey districts (DR) has been considered as a primary unit (UP); in other words, a primary unit is then defined as an average-sized geographic area with 300 households, characterized by clear limits that allow for field-localizing it, without any ambiguity.

The 1994 population survey districts allowed thus to set up a survey basis made up of 14 948 stratified primary units (8 533 in the city and 6 415 in the countryside).

Master-sample survey basis units have been stratified. Stratification is so desirable that it enables the various users making survey plans that meet efficiently their surveys' objects by ensuring:

• Optimum sample size;
• A significant cost cut ;
• A substantial improvement of estimators' accuracy.

To free oneself from drawdown contingencies, a first dichotomous stratification, which we introduce generally in survey plans in Morocco, is the distinction between the urban and the rural, insofar as socioeconomic phenomena are not the same in both of them. On the other hand, it should also be noted that survey unit's stratification criteria vary according to the residence environment. Used criteria are:
i) Administrative tranching of the national territory into regions and provinces
ii) Predominant « housing standard » for urban zones. These criteria allowed for distinguishing the following five strata: "luxurious", "modern", "old medina", "new medina" and "underground" (including precarious housing).

Survey plan follows one degree stratified sampling principles with remission unequal probabilities. Primary units of the survey basis within each residence environment have been proportionally divided according to the various strata in each environment.

The scheme allowed therefore for making up a 1 575 primary units (911 in the city and 664 in the countryside) master-sample.

Main features of the ENCDM 2000/01 survey plan :
The sample of the concerned survey has been taken from the master-sample and follows two degrees stratified sampling principles. This kind of survey shows more than one advantage. It reduces the survey cost and allows also for improving coverage, works field supervision and the quantity of collected data. Sample selection work can also be reduced.

However, the main drawback is that this survey relatively reduces the sample's efficiency.

The main characteristics of the ENCDM 2000/01 survey are the following:
i) Survey unit : the l'ENCDM 2000/01 survey plan involved a sample selection in two stages :

• first degree : it is about the above-defined sample primary units. For ENCDM needs, a 1250 primary units sample has been selected among the 1575 of the master-sample, i.e. 710 urban units and 540 rural ones
• second degree : the « household » has constituted the secondary unit of the applied survey. Within the framework of the elaboration of the master-sample, lists of households from the various primary units have been established. At the level of each primary unit, a systematic drawdown allowed for selecting 12 households.
  ii) Sample size : considering budgetary constraints and the issues linked with the available human and financial means, the sample size is set at 15 000 households. This size was considered sufficient to have reliable estimates according to the residence environment (urban/rural), different socioeconomic categories of the country and the most important regions and provinces (in terms of population).