APPLICATION OF CONFIDENTIALITY RESTRICTIONS

9.40 The manner in which confidentiality is applied to international merchandise trade statistics can cause negative values to be displayed in some outputs. The following paragraphs describe why negative values exist and why they are important. The information is complex but is essential for users who purchase the complete international merchandise trade dataset and do their own data extractions and manipulations. Users of time series spreadsheets or data cubes and users who purchase specific commodities, countries or other components of the data will never see negative values.

9.41 During output processing, four different types of output records are created to protect confidential trade and ensure the most amount of data can be released. The four types of records are:

• records providing information on trade not subject to confidentiality restrictions (type i)
• records enabling the release of the greatest possible level of information on commodities subject to confidentiality restrictions (type ii)
• records enabling the release of the greatest possible level of information on trade with countries, relating to Australian states, or passing through overseas or Australian ports, where confidentiality restrictions apply to these items (type iii)
• records derived from record types ii and iii above, which serve as balancing items, so that totals can be easily and accurately calculated for items which are subject to confidentiality restrictions (type iv). These records have negative values.

9.42 For records involving commodities not subject to confidentiality restrictions, only one output record is created (type i). This record is identical to the aggregates of records prior to the application of confidentiality.

9.43 For records involving commodities which are subject to confidentiality restrictions, two different output records (types ii and iii) are created in order to replace a single input record. This is the extent to which confidential data are suppressed.

9.44 Replacing a single input record with two output records means that, if no further action were taken, there would be some double counting in reports which list trade in all commodities with all countries. The type iv record overcomes this problem by offsetting the double counting that would otherwise occur.

9.45 To illustrate by example, with a 'No country details' restriction, only the country (and port) data should be concealed. By creating a type ii record, the value, quantity and commodity details are preserved for outputs that do not include country or port information. By creating a type iii record, country and port details are preserved for outputs that include country and port information, but commodity details are suppressed. The value and quantity are included in 'Combined confidential items'. The type iv record is created to avoid double counting in totals.

9.46 The above held true for all commodity codes with confidentiality restrictions prior to the changes introduced in September 2008 for imports and import clearances, and June 2013 for exports. From these dates, the offsets described above are true for commodity codes with restrictions of 'No country details', 'Selected country details', 'No state details' and 'Selected state details'. However, for commodity codes with a 'No commodity details' restriction, only the type ii record is created. This means the offset record that overcomes double counting is not needed to protect confidentiality as only one output record is created.