[is] withholding the values of certain cells in tabular data from publication. This means that their value is not shown in the table but replaced by a symbol such as "×" to indicate the suppression.
[occurs] if data is from a sample survey then it may be inappropriate to release tabularoutputs with cells which contain small numbers of individuals, say below 30. This is because the sampling error on such cell estimates would typically be too large to make the estimates useful for statistical purposes. In this case, suppression of cells with small numbers for quality purposes acts in tandem with suppression for disclosure purposes.
Cell suppression has drawbacks. It creates missing data, which complicates analyses because the suppressed cells are chosen for their values and are not randomly distributed throughout the dataset. When there are many records at risk, as is likely to be the case for spatial data with identifiers, data disseminators may need to suppress so many values to achieve satisfactory levels of protection that the released data have limited analytical utility. Cell suppression is not necessarily helpful for preserving confidentiality in survey data that include precise geospatial locations. It is possible, even if some or many cells are suppressed, for confidentiality to be breached if locational data remain. Cell suppression also does not guarantee protection in tabular data: it may be possible to determine accurate bounds for values of the suppressed cells using statistical techniques. An alternative to cell suppression in tabular data is controlled tabular adjustment, which adds noise to cell counts in ways that preserve certain analyses.