Methodology
Sample establishments
Geographical scope
A total of 56 cities have been selected, as follows:
- The 52 Spanish provincial capitals.
- The four cities with populations exceeding those of their respective provincial capital (indicated in red on the attached map). These cities are Vigo, Gijón, Talavera de la Reina and Jerez de la Frontera.
The selected cities represent over 36% of the population of Spain.
Establishment types
Within the geographical scope described above, a representative sample of retail sales outlets has been selected.
Three main types of retail trade have been distinguished: Organised distribution, specialist trade and municipal markets.
- Organised distribution: Within this group there are five different types of establishment::
- Hypermarket: Retail establishments offering other product categories in addition to food, toiletries and household products. Normally they have a floor area in excess of 2,500 m2.
- Large supermarket: Retail establishments selling food, toiletries and household products with a floor area equal to or greater than 1,000 m2.
- Medium-sized supermarket: Retail establishments selling food, toiletries and household products with a floor area covering between 400 and 999 m2.
- Small supermarket: Retail establishments selling food products, whether self-service or grocery stores, with a floor area covering between 50 and 399 m2.
- Discount store: Retail establishments selling food, toiletries and household products with a limited range, high level of penetration of the distributor's brand, and a permanent policy of low prices.
- Specialist shop: Establishments specialising in the retail of fresh food or household goods. By nature there is no set limitation in terms of floor area, though four different types can be distinguished:
- Fishmonger's shops
- Butcher's shops
- Greengrocer's shops
- Household goods shops
- Municipal markets: Establishments specialising in the sale of fresh food, located in municipal markets. There are different types:
- Fishmonger's shops
- Butcher's shops
- Greengrocer's shops
Other types of establishment have not been considered, because:
- The product range is not uniform or is insufficient for comparison with other establishment types. This is the case with supermarkets having a floor area smaller than 50 m2
- They have particular features in terms of accessibility, type of sale or commercial characteristics, as is the case with itinerant trade, street markets, cooperatives and convenience stores.
Selection criteria
Establishments have been selected by differentiating between the larger types of retail trade as described above.
Organised distribution
Selection of establishments is carried out using census information from Alimarket. Different selection criteria are established for hypermarkets and supermarkets on the one hand, and discount stores on the other.
Hypermarkets and supermarkets
The sample selection was made following two basic criteria:
- Regional representation: To audit a minimum of 65% of the floor area of the hypermarkets and supermarkets in each city, and over 70% overall (combining all 56 cities)
- Retail brand representation: The basic criterion is to cover the greatest possible number of retail brands, giving priority to those with a bigger nationwide presence. For the latter, it is envisaged that a minimum of 50% of their floor area will be audited in the cities subject to study. In this sense, a distinction has been made between:
- Nationwide retail brands: Those present in at least six of Spain's autonomous regions, with a share of floor area in excess of 1%. There are a total of 13 retailers.
Tabla enseñas de ámbito estatal Enseña CCAA Share%m2 Carrefour 16 16,65 Mercadona 15 10,09 Alcampo 14 6,57 Eroski 17 6,29 Hipercor 10 4,87 Eroski Center 14 4,48 El Corte Ingles 15 1,73 Maxi-Dia 14 1,52 Supercor 11 1,21 Carrefour Express 10 1,08 El Árbol 7 1,85 Supersol 7 1,44 Sabeco 6 1,15 - Regional retail brands: Those with a share equal to or greater than 0.5%, regardless of geographical coverage. There are a total of 19 retailers.
Tabla enseñas ámbito regional Enseña CCAA Share%m2 Caprabo 2 1,93% Supermercados Consum 2 1,62% Gadis 2 1,55% M.A.S 1 1,46% Galerias Primero 3 1,43% Alimerka 2 1,24% Condis 2 1,12% Ahorramas 2 0,91% Supermercado Piedra 1 0,90% Froiz 2 0,89% Lupa 2 0,83% E. Leclerc 4 0,82% Coviran 7 0,81% Dia Market 12 0,80% Sup. Consum basic 4 0,79% El Jamon 1 0,78% Hiper dino 1 0,70% Super BM 3 0,52% Sorli Discau 1 0,50%
- Nationwide retail brands: Those present in at least six of Spain's autonomous regions, with a share of floor area in excess of 1%. There are a total of 13 retailers.
All hypermarkets situated within the area of influence of a city subject to the Observatory study, have been selected.
Discount stores
The selected sample represents more than 40% of the floor area of each of the three main discount retailers in the audited cities.
| Enseña | CCAA | Share%m2 |
|---|---|---|
| Dia | 18 | 5,57% |
| Lidl | 17 | 2,70% |
| Aldi | 8 | 0,58% |
Specialist shop
Generally speaking, as there is no reference census, selection has been made considering the distribution of establishments in different areas of each city, with a ratio of six stores for each type (greengrocer's, butcher's and fishmonger's), with the exception of household goods stores, of which three were selected for each city. Nevertheless, in some cases the smaller retail range on offer may necessitate some slight adjustments in said distribution.
Municipal markets
Municipal markets were selected on the basis of the census published by the Ministry of Economy and Finance in the book Centros comerciales y mercados minoristas (Shopping Centres and Retail Markets).
For each market a total of 12 stalls, including greengrocer's, butcher's and fishmonger's, will be audited. As a rule, prices are taken from the main municipal market of each city. However, it must be remembered that:
- Two markets have been selected in A Coruña, Bilbao, Zaragoza, Valladolid, Seville, Córdoba, Málaga, Valencia and Tarragona
- Three markets have been selected in Madrid.
- Four markets have been selected in Barcelona.
- There are no municipal markets in Huesca, Teruel, Talavera de la Reina, Ceuta and Badajoz. As with specialist trade, the small number of stalls in some markets may result in modification to the final distribution of stalls.
Fieldwork
Professional team
Fieldwork will be carried out by 336 observers (averaging roughly six per city) with extensive experience in this type of study. There will also be 28 coordinators (one for every two cities) who will be responsible for supervising the observers, planning visits to sample outlets, addressing queries or problems that may arise during fieldwork, collecting questionnaires and so forth.
Procedure
Survey takers will have planning information for the sample outlets due to be visited at their disposal. This will include basic details of the establishments for which prices must be taken (address, retail brand, size, manager - contact person, etc.).
The survey takers shall visit the selected establishment and complete the questionnaires directly and anonymously. If necessary, they will introduce themselves to the owner, manager or other persons responsible for the establishment, providing their accreditation so that they may be authorised to take prices. Once authorised, survey takers will proceed to fill out the questionnaire, noting down the prices of the products listed therein, according to the characteristics indicated (product type, brand, size and equivalent product in the home-brand category).
In the event that the establishment's managers do not authorise the survey taker to collect prices, the latter will notify the field coordinator. The coordinator will contact the establishment with a view to obtaining authorisation, explaining the objectives of the study and making available any documentation that may be requested (study introduction letter, survey taker's accreditation documents, etc.).
Upon conclusion of the fieldwork, a report will be drawn up that includes any problems or issues raised during the execution of fieldwork.
Replacement of establishments
Establishments withholding authorisation for the taking of prices will be replaced. This is also the case in respect of establishments that are closed (temporarily or permanently), those that have switched retail brand, and those that do not correspond to the type of establishment for which they were selected, at the time of the fieldwork.
Replacement establishments shall be of the same type and retail brand, and shall be located in the same city.
In the event that there is no replacement establishment of the same type/city, an establishment of a different retail brand shall be chosen, in accordance with the overall progression of the study, so that any problems arising have minimal impact on the representative nature of the sample, whether in terms of retail brand, city, type of sale or autonomous region.
Supervision and control
The work of all survey takers shall be monitored by the field supervisors. Their function is to carry out random monitoring of the field personnel, without the latter being informed that they are being monitored, in order to ensure that prices are taken correctly.
In addition, supervisors will make checks in person at 20% of the establishments visited.
Timming
The fieldwork shall commence once the field team's training has been completed.
This shall be for a maximum duration of two weeks.
Data processing
The fieldwork shall commence once the field team's training has been completed. This shall be for a maximum duration of two weeks.
Calculating the prices of individual establishments
In calculating the prices of the different product families and sub-families, the aspects below, relating to the idiosyncrasy of the study, shall be taken into account
The objective is to minimise the influence that these factors may have, and to obtain comparable results. The following criteria shall be used when calculating prices
Missing values
In the event that a price is missing for a certain product, even where over 50% of the products in a family or sub-family are available, the said value shall be completed using the average price of this product in establishments of the same retail brand, in the same city as the establishment in question. In the event that this data is unavailable, the average price of the product in the city shall be used, regardless of retail type.
The same process shall be used when one or two sub-families is missing in the calculation of “total food” and “total packaged food".
The price for each establishment, for each family and sub-family, is the weighted average of the prices of products considered. In this case, the weight in the Retail Price Index for the year 2008, adapted to the product range in question, shall be used for weighting. In the event that there is more than one product within the same sub-class, the weight shall be distributed equally for each of the products that make up the sub-class.
Calculating the prices of commercial types by city
ABased on the individual prices of the different establishments, the latter will be grouped together by commercial type. The following process was used, depending on the commercial type, to make this calculation
Calculating the prices by city
Based on the prices of the different commercial types, the prices of each product family and sub-family are calculated for each city. These prices correspond to the weighted average of the different commercial types. In this case, use is made of the percentage of sales by channel for each of the commercial types, based on data from the Ministry of the Environment and Rural and Marine Affairs and from the AC Nielsen annual mass-market retail trade survey.
Calculating the prices by distribution retailers
Based on the prices of individual establishments, the price is calculated for each retailer.
The calculation of prices by retailer is performed by using the weighted average of all establishments within the retail brand, using the floor area of each establishment as a weighting factor, according to the retail distribution census conducted by Alimarket.
Calculating the relative indices
An index of 100 is granted to the establishment (type, city or retail brand) with the lowest weighted-average prices; the other establishments are indexed in reference to this. As such, all relative indices are equal to or greater than 100.
Calculating quarterly price variations
Quarterly prices variations express, in percentage terms, the price difference between the present and the previous quarter for each type, city or retail brand. Variations therefore appear as negative values when the prices have fallen, and positive values when they have risen.
Calculating the historical evolution
The index of 100 is granted to the price for each type, city or retail brand in the first quarter of 2009. Present-quarter prices for each type, city or retail brand are then indexed accordingly. For this reason, the present indices are situated around the 100 mark, falling below this figure when prices are lower than in the first quarter of 2009, and rising above 100 when they are higher.
