Small area estimation results are also available on the following interactive map:
The structural population survey provides important information on the population, including information about work. By means of a sample survey of at least 200 000 people each year in Switzerland, it is possible to make reliable estimates of the economic activity rate of groups of 15 000 inhabitants.
By combining the surveys of several years (pooling over three or five years), it is possible to reduce this limit to groups of 5000 or 3000 people. This can be done using standard methods.
It should be noted that in 2014, Switzerland had almost 2300 communes. Of these, 80% have fewer than 5000 inhabitants and 70% fewer than 3000.
The question addressed here is whether it is possible to reduce the limits mentioned above even further to produce reliable estimates by means of new methods that are based on statistical models, which use information that is available for the whole population.
The whole purpose of Small Area Estimation (SAE) is to push the boundaries imposed by standard methods by using techniques based on modelling which make use of complementary information on the population.
Professor I. Molina from the University Carlos III of Madrid, a specialist recognised internationally for this type of methods, was commissioned to examine the possibility of obtaining reliable estimates of the economic activity rate at commune level. This study, based on the 2012 structural survey and on OASI (Old-age and survivors’s insurance) data from 2011, showed that it is possible to obtain reliable estimates for both annual economic activity rates, as well as their precision (design MSE), for communes that had a sample of at least 100 people, i.e. considerably smaller than when using standard methods.
Following the encouraging results obtained with the SAE methods using the 2012 structural survey and OASI data from 2011, the FSO then continued the study by investigating the possibility of combining this information with data pooled from the structural survey over several years. Specifically, these estimates refer to an average target population from the structural survey, in this case over the three years 2012–2014. The main reason is the possibility of obtaining reliable estimates for a larger number of communes than can be obtained from annual surveys because the lower limit of 100 persons in the sample remains a priori the same for the data pooling.
Based on the conclusions of the study commissioned to Professor I. Molina, for the structural survey the FSO decided to publish only estimates for communes with a sample of at least 100 people. To have a sufficiently large sample and to be able to publish results for as many communes as possible, results are based on structural survey data pooled over three years, i.e. from 2012 to 2014. In contrast to standard methods, which enable results to be published for only 20% of communes, it is now possible, thanks to these new methods, to triple this figure, covering 60% of communes. At the end of 2014, this represented 80% of the permanent resident population in Switzerland aged 15 and over.
The results can be found in the table below:
Results should be interpreted with caution, as they are estimates based on an average population in the structural surveys of 2012, 2013 and 2014.
A number of questions remain open, posing methodological challenges to be met:
- Can the model be further improved?
- What is the best number of years for data pooling?
- What impact does pooling have on estimating precision (design MSE)?
- What is the best selection of OASI data to use?
In future we hope to respond to the methodological challenges mentioned above but also to explore the possibility of using small area estimation in other FSO surveys. This will involve examining if and how these methods could best be applied to business surveys in which the small area would no longer be geographical but of a different nature (detailed level of economic activity for example).
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