Items and services paid for by households were chosen if they had a significant weight within each sub-group and were bought and sold with some degree of regularity and in sufficient quantities to allow price quotations to be obtained with adequate precision.
The weighting for the other items and services in the sub-group was assigned on the basis of similarity, or proportionally within the sub-group. Two items or services can be considered similar if one can be substituted for the other and if their change in price is comparable. Thus an article which has not been selected but which is similar to a selected article is given the weight of the latter, while the weight of other articles is spread proportionally throughout the sub-group.
| Major groups | Number of items | Weights | Approximate number of price quotations |
|---|---|---|---|
| Food | 205 | 40.1 | 72500 |
| Clothing and footwear | 111 | 9.4 | 7900 |
| Housing: | @ | @ | @ |
| Rent | 1 | 2.3 | 400 |
| Repairs and maintenance | 13 | 2.0 | 800 |
| Fuel, light and sanitary services | 5 | 4.2 | 200 |
| Household equipment | 84 | 8.6 | 12300 |
| Medical care | 31 | 7.2 | 1600 |
| Transport and communication | 23 | 11.4 | 800 |
| Education and recreation | 61 | 8.9 | 4800 |
| Miscellaneous goods and services | 23 | 5.9 | 4700 |
| Total | 557 | 100.0 | 106000 |
Forty seven shopping centres were chosen, 21 in the Federal Capital and 26 in the suburbs of Buenos Aires; 140 sub-samples of stores were chosen from all the outlets in these centres, which are visited once a month.
In order to determine the number of respondents for each variety, the geographical area covered by the index and the variability of the price were taken into account. The sample of outlets is revised periodically in order to incorporate new marketing techniques and possible changes in the geographical distribution of the stores.
The prices of items and services are recorded every working day of the month, that is, the sample of outlets for a specific item or service is distributed throughout the working days of the month (excluding Saturdays, Sundays and holidays).
Most of the prices are recorded by means of personal contact, the telephone being used only for certain services for which quality does not often change and for which telephone surveys give a good response.
For services subject to state price control (electricity, gas, sanitary services, public transport, etc.); the days of the month when the price comes into force are used. The cash price is recorded for the various items and services.
Given the many possible interpretations of the term rent
,
quotations are recorded for the following rented dwellings:
occupied family dwellings, unfurnished flats, houses,
apartments, permanent living quarters in residential hotels and
leased property dwellings for which the rent is paid in national
currency, dwellings in which the rent does not cover services,
and rented dwellings that are not dependant on an employment
relationship. The amount of rent is recorded as well as
other data on the dwelling and the contract, which help to verify
the declared value and to detect when there are changes in the
quality of the dwelling.
family shopping basket, a detailed description must be given of all characteristics determining the existence of different prices at a given moment, and the extent to which changes in these characteristics are imputed to price variations for practical purposes. Details of the variety are usually necessary for each respondent (make, model, size, etc.) to ensure the comparability of subsequent price quotations.
Two kinds of definition have been adopted to specify items. First, for homogeneous varieties, equivalent products are quoted in the various outlets, enabling a significant average price to be calculated (butter, roast meat, eggs, oranges, chard, bar of soap, etc.). Secondly, for heterogeneous varieties corresponding to an incomplete specification, the description of the product is specific to the outlet. It is extremely useful to use heterogeneous varieties, e.&g for clothing, so as to reflect differences from one store to another and changes in fashion (footwear, clothes, television, education, rent, etc.).
If there are no overlapping price quotations to compare quality, a quality adjustment is made in the price of the new variety so that it can be compared with the former.
Seasonal items include all items and services for which the quantity consumed and prices vary significantly throughout the year. Generally, it is fluctuations in supply (vegetables, fruit, etc.) or demand (winter and summer clothing, etc.) that lead to a temporary disappearance of the item.
The indexes of each basic aggregate (minimum level of expenditure detail for which the weighting is constant) are estimated using a sample of prices from a specific group of items or services from an established group of outlets.
The method used to calculate the price relative of an item depends on whether it is considered a homogeneous or a heterogeneous variety. For homogeneous varieties, the price relatives for the current and previous periods are used. For heterogeneous varieties, the average of price relatives for the various outlets is used.
Supermarkets, department stores and other retail outlets are assigned weights according to their estimated retail sales volume. The weights are used to calculate the relatives of average prices or the averages of price relatives.
Estadística mensual(Buenos Aires).
Idem: Indice de precios al
consumidor, Revisión base 1988 = 100, Sintesis metodológica
.