Major groups | Number of items | Weights | Approximate number of price quotations |
---|---|---|---|
Food | 67 | 5902 | ... |
Clothing | 13 | 959 | ... |
Household furnishings | 18 | 277 | ... |
Personal and medical care | 16 | 401 | ... |
Fuel and light | 4 | 437 | ... |
Construction materials | 10 | 403 | ... |
Vehicles | 8 | 491 | ... |
Tobacco | 4 | 59 | ... |
Housing | 2 | 770 | ... |
Personal services | 4 | 93 | ... |
Other services (incl. transport and travel) | 9 | 208 | ... |
Total | 155 | 10000 | ... |
It includes own-production and own-consumption (especially as regards agricultural products). These goods and services are estimated by assigning them fictitious or conventional prices (the market price in the nearest consumer market).
Rent and minor repairs to the dwelling (repair of adobe walls with cement) are included as consumer expenditure, but not the purchase of a dwelling, even with monthly payments, nor the addition of a room.
Also excluded are direct taxes, miscellaneous contributions and gambling. On the other hand, indirect taxes included in prices paid by consumers are included in the index.
In many households, certain family members are self-employed or own-account workers (agriculture, industry, crafts or trade). Any related supplies are obviously excluded from the household's final consumption expenditure. Also excluded from the monthly index is expenditure for which either there is no information on prices, or for which the prices noted do not conform strictly with the definition of the item considered.
The asking price (quoted by the trader or artisan) differs from the average price actually paid by the consumer. The difference between these two prices is variable: it is lowest for furniture, clothing and household appliances, and highest for food. A similar difference is presumed to exist for cereals and non-food items in the index.
For a homogeneous variety, prices are generally similar. Thus, an average price (the average of the prices found in each of the survey outlets) makes sense. The index for the variety in N'Djamena is then equal to the average price relatives for this variety between the two periods. However, the current index uses the simple arithmetic average of the basic indices.
For a heterogeneous variety, products may differ considerably, and cannot necessarily substitute for each other. The concept of an average price therefore makes little sense. Nevertheless, it is possible for each product, e.g. three kinds of pants, to compute a basic index equal to the price relative of the product in an outlet in the base period. The index of the variety in N'Djamena is therefore equal to the simple arithmetic average of the basic indices.
rule of threemethod); (c) the price is linked to several of the product's characteristics. For simplicity, it is possible to focus on one of the characteristics and thereby use alternative (b). It is also possible, by using a so-called
econometricformula, to shift from the product's characteristics to its value; this is the
regressionmethod.
Once incorportated into the index, the new product is considered
to replace
, in whole or in part, one or more products in the
index. This means integrating the new product in an existing
category, through the creation of a variety.
Evolution des prix à la consommation dans la ville de N'Djamena.
Idem: Indice des prix à la consommation 1983-1989
, February
1990.