Setting Up the Frame - Sampling Spatial Units for Agricultural Surveys - page 96

materials used for the survey and the information collected help to reduce
non-sampling errors in interviews and are a good basis for data imputation for
non-respondents.
• Reduced burden on farmers.
• They allow the use of spatially defined auxiliary information (e.g. GIS data, see
Chap. 3 , and remote sensing, see Chap. 4 ) .

Spatial frames have also some disadvantages:
• Cost . The setting up of the frame is usually a high cost activity (not so high for
point frame), and there are high sample selection costs above all in the case of
units with identifiable physical boundaries. Also, face-to-face interviews
conducted by well-trained enumerators are very costly (Cotter et al. 2010 ), and
high-tech methods, qualified office staff, and statisticians are needed.
• They are not suitable for cultivations with high spatial variability (scattered), and
they have a limited precision of the estimates for small areas or highly concen-
trated land cover/land use classes.
• Cartographic material is required to construct the frame (such as maps, satellite
images, aerial photos).
• They can be less efficient than a list frame as the only stratification is for land
cover/land use. They can also be inefficient for commodities on large farms or
commodities that are rare (Fecso et al. 1986 ; Vogel 1995 ).
• They are sensitive to the impact of outliers, and the estimates may be unstable
(Pratesi and Carfagna 2013 ).

5.4 Frame Construction

Frames construction is very different depending on the definition of statistical units
used. List frames are formed by lists of holdings or holders addresses and derive

from previous agricultural, housing or population censuses, from lists set up by
political or administrative subdivisions, from farmer ' s associations or from other
administrative data sources (Wallgren and Wallgren 2007 , 2010 ). They contain
information on holding size, crops, livestock, and other characteristics. These types
of information are often used to stratify the frame that greatly improves sampling
efficiency (see Sect. 6.5 ). The main advantage of list frame surveys is that they are,
for certain aspects, more efficient, since sampled farms provide in one interview a
large amount of information on crop area and yields, livestock, inputs, or socio-
economic variables.
There are many different ways of preparing a list of agricultural holdings. Local
knowledge should be used to list not only farm households, but also holdings under
different legal status, such as cooperatives, government farms, and enterprises
(FAO 1995 ). In the case of countries, which have and keep up-to-date land records
(a cadastre), it may be easy to prepare a frame through reference to the land records.
In the land records the name of the holder is normally entered together with all the

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