The working universe of data considered in this study was composed of the microdata included in the Agricultural Census of 1999 that corresponded to the region of Galicia. Each farm was characterized by the following items: farm identification, holder, legal personality and management of the farm, total area and farming system, type of tenure, irrigation, land uses, arable crops and fallow land, kitchen gardens, woody crops, greenhouse and mushrooms, set-aside of arable land under the support system of the European Union, successive secondary crops, combined cropping, machinery, livestock, storage facilities for natural fertilisers of animal origin, family labour force, non-family labour force, working days of farm work undertaken by persons not employed directly by the holder, and production marketing (MAPA, 2002).
An operational procedure was developed in order to group farms with common characteristics (type and size) and to determine the spatial distribution of farms (location) in a systematic manner. After the different groups were established, each group could be characterized separately (based on data from the Agricultural Census), further information could be searched, and representative samples could be selected in order to carry out targeted surveys (focused on production processes, yield and consumption).
Fig. 1 describes the information search process. ‘Typology’ refers to the establishment of groups of farms that were composed of a particular combination of productive land uses that caused differences in the technical-economic results of the farm as compared to other combinations. ‘Classification’ consisted in grouping farms into size classes that were representative of the different production levels. In the final characterization, the values that resulted from combining the information obtained from surveys and from the Agricultural Census were assigned to the variables included in each land use and size group.