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A cell is regarded as confidential, if the n largest units contribute more than k % to the cell total, e.g., n=2 and k=85 means that a cell is defined as risky if the two largest units contribute more than 85 % to the cell total. The n and k are given by the statistical authority. In some NSOs [national statistical office] the values of n and k are confidential.
NIST SP 800-188 from OECD Glossary of Statistical Terms