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Eurostat disseminates a high number of statistical tables on its website and through specific user requests. All these tabular data are treated for primary confidentiality. Primary confidentiality concerns tabular cell data, whose dissemination would permit attribute disclosure. The two main reasons for declaring data to be primary confidential are: too few contributors in a cell and dominance of the first n largest contributors in a cell <a href="#conf" aria-describedby="footnote-label" id="conf-ref"></a>. 

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For non-confidential cells, the extrapolated number of holdings and all values of characteristics variables in cells are rounded to the closest multiple of 10.

Because of the confidentiality treatment, the sum of the individual cells does not systematically match with the value of the "total" cell.

The Eurobase tables in SAS present the standard FLAG_CODE=A for the cells that are to be suppressed because of the threshold rule. In the code list on "confidentiality status" defined by the SDMX Statistical Working Group <a href="#sdmx" aria-describedby="footnote-label" id="sdmx-ref"></a>,, the flag A stands for <em> "Primary confidentiality due to small counts" </em>.

Limitations to the application of secondary confidentiality

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• the numerous tables disseminated on Eurostat website and through ad-hoc requests;
• that the whole publication programme should be reviewed in an integrated way. When a new table is created, the other tables need updating.
• the suppression of cells should have the same pattern for different reference periods. A value for a confidential cell from other reference periods is usually a good basis for estimating and therefore disclosing data.

It is to be noted that:

• The rounding to the nearest multiple of 10 would prevent recalculation of the exact values to some extent.
• When data are estimated from a sample, estimated values deviate from the true values, which would additionally prevent recalculation of the exact values to some extent.

Eurostat<a href="#recal" aria-describedby="footnote-label" id="recal-ref"></a> made an analysis of the possibility for recalculations and found in 1993 that:

• most of the derived values are not reliable; there are negative solutions and solutions outside an interval of ±50% in relation to the true value;
• a few derivations come very close to the real value.

It was concluded not to suppress data in cells, because "the procedure involves iterations of treatment of derivation while no possibility of derivation can be realistically excluded. It also entails loss of data involving no risk of disclosure". Besides the methods already implemented (suppression, rounding) or discussed in the above table, there are other methods e.g. table redesign (collapsing rows/columns), controlled tabular adjustment (selectively adjust cell values: unsafe cells are replaced by either of their closest safe values; other cell values are adjusted to restore additivity), perturbation (add random noise to cell values). Application of methods have pros and cons. For deciding on the most suitable solution, a balance has to be struck between confidentiality and reliability i.e. to which point the confidentiality treatment is effective and does not jeopardize the accuracy and usability of the results, unnecessarily.

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    <h2 class="visually-hidden" id="footnote-label">Footnotes</h2>
    <ol>
      <li id="risk"> European Business Statistics Manual. <a href="https://ec.europa.eu/eurostat/statistics-explained/index.php?title=European_business_statistics_manual_-_Statistical_Disclosure_Control#SDC_rules_and_methods_for_tabular_data_" target="_blank"> See https://ec.europa.eu/eurostat/statistics-explained/index.php?title=European_business_statistics_manual_-_Statistical_Disclosure_Control#SDC_rules_and_methods_for_tabular_data_</a>. <a href="#risk-ref" aria-   label="Back to content">↩</a></li>
<li id="conf"> 
Handbook on Statistical Disclosure Control, version 1.2, Jan 2010. <a href="https://ec.europa.eu/eurostat/cros/system/files/SDC_Handbook.pdf" target="_blank"> See https://ec.europa.eu/eurostat/cros/system/files/SDC_Handbook.pdf</a>. <a href="#conf-ref" aria-   label="Back to content">↩</a></li>
<li id="sdmx"><a href="https://sdmx.org/wp-content/uploads/CL_CONF_STATUS_1_3_2022.docx" target="_blank"> https://sdmx.org/wp-content/uploads/CL_CONF_STATUS_1_3_2022.docx</a>. <a href="#sdmx-ref" aria-   label="Back to content">↩</a></li>
<li id="recal">Eurostat (1993). "Safeguard of statistical confidentiality: outline of practical and statistical measures". Working Party "Statistics of the structure of agricultural holdings of the Agricultural Statistical Committee". Meeting on 14 and 15 January 1993, Luxembourg. <a href="#recal-ref" aria-label="Back to content">↩</a></li>
    </ol>
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