ESENER-PSR 2009 - European Agency for Safety and Health at Work

at least rough information (size-class) on the number of employees for each address
a telephone number for each address 7
The address-source to be used had to contain information on both the size-class and the
sector of activity for each listed address. If this information (or part of it) is lacking, it is
extremely time-consuming and costly to carry out interviews according to the set stratification
matrix:
If an address-register contains information on the size-class, but not on the sector of activity
each address belongs to, the only criterion for a pre-selection of the addresses and for
drawing the sample is the size-class. In such a case, a random sample has to be drawn from
all establishments listed within a size-class and information on the sector has to be collected
during the interview-phase by inserting a question about the main activity of the contacted
establishment into the questionnaire. The answers to this question then have to be regularly
coded in order to enable a daily count of the realized interviews by sectors and size-classes.
While this procedure works fairly well at the beginning of the field-phase, difficulties begin as
soon as the first cells (defined by the size-class and by the information about the sector as
given in the interview) are completed. From this point on, all further interviews have to be
filtered to “end” if the chosen respondent belongs to a cell where the required number of
interviews is already accomplished. Further interviews can then only be realized in the
remaining “open” cells. With each completed cell, it gets more and more difficult to fill the
remaining cells, as the number of contacts with establishments of sectors which are not
needed any more is continually rising. For the completion of the last few cells, an enormous
amount of futile contacts is almost inevitable.
Missing information about the number of employees is still more problematic. In principle, an
equivalent procedure as described above for registers without information on the sector of
activity could be applied. Yet, as establishments with less than 10 employees – which are the
vast majority of all existing establishments - are not included in this survey, a very large
number of interviews would have to be filtered to “end” because the contacted establishments
do not surpass the size-threshold. This problem is even much more accentuated in a
disproportional sample-design as applied in this study (for details about the dimension of such
futile contacts see chapter 4.1.3., step 4).
1.5 Coverage of sectors of activity: The Public Sector as specific challenge
Including all sectors of activity in a survey of establishments has the evident advantage of
getting data that represent the situation in the whole economy. In practice, however, only very
few establishment or company surveys really cover the whole economy without any limitations
as regards the sectors of activity. Certain sectors or sub-sectors like e.g. the Public
Administration are mostly not included. Sometimes, the exclusion is based on reasons of
7 Or at least the possibility to add telephone numbers to the (randomly selected) gross sample for the
study.
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