Information provided in statistical and administrative collections does not always comprise the exact words used as the official names of classification categories in the SACC. A coding index is therefore necessary to act as a link between individual responses or items of information and the classification categories, enabling data to be coded accurately and quickly to the appropriate category in the classification.

The coding index for population statistics has been developed to assist in the implementation and use of the classification and should be used when coding responses to questions relating to country of birth, country of origin, etc., or information from other sources that relates to countries. The coding index has been devised by reference to relevant documents such as atlases, gazetteers, guides to countries, and most importantly, by analysis of ABS data collected over many years. It is thus based on information actually obtained in ABS statistical collections. The coding index provided in the ASCCSS has been refined and updated for the SACC following its use in the 1996 Census. It contains a comprehensive list of the most probable responses to questions relating to country and their correct classification codes. It also assists in the accurate and timely allocation of country codes for data originating from other sources (see Appendixes 4 and 5 for the population statistics coding index in alphabetical and numerical order).

A coding index specifically designed to assist in the allocation of country codes to economic data is also included in the SACC. This index has been developed for the following reasons:

• A number of geographic entities required in the collection of economic data have been allocated supplementary codes not used when coding the same entity for population statistics. For instance, Christmas Island is allocated the supplementary code 0706 for international trade statistics, but is allocated the main classification structure code 1101 (Australia) for population statistics such as country of birth.
• A number of geographic entities required in the collection of economic data consist of two or three countries combined. These entities are allocated supplementary codes not used in population statistics where the main classification structure codes of the individual countries are used. For instance, data relating to 'Belgium and Luxembourg' are allocated the supplementary code 0704 for international trade statistics. For birthplace statistics responses are allocated either the code 2302 (Belgium) or 2306 (Luxembourg). A single index containing all this information would be confusing and create the potential for error.
• A number of non-geographic entities which are needed for the collection of economic data have been allocated supplementary codes which are not required for population statistics. For instance, 0718: International Capital Markets is needed for balance of payments statistics.
• Many of the entities included in the population statistics index which relate to the idiosyncratic responses of individuals are not required when coding economic statistics by country. This 'clutter' has been removed from the economic statistics coding indexes.

• the standard set of countries and country groupings included in the main classification structure;
• the economic supplementary codes for inadequate data;
• the supplementary codes for economic and political country groupings;
• the supplementary codes for economic and other entities; and
• the supplementary codes for the main classification structure.

The following rules relate to the coding of information provided by individuals when asked questions about their country of birth, country of origin, etc. The principles used can be applied to information about countries, regions, areas, etc. emanating from other sources which need to be allocated a country code. The rules can be applied to either the economic statistics or population statistics index.

When coding responses in statistical or administrative collections for population and social statistics, responses which match exactly with an entry in the coding index are assigned the code allocated to that index entry. When responses do not match exactly with an index entry the following rules should be followed. (Some of the examples used do, in fact, appear in the coding index, but are given for illustrative purposes.)

Responses which relate directly to a country category but which contain information additional to that included in the coding index are allocated the code of that country category. Such instances include responses consisting of a full or formal country name (for example, Syrian Arab Republic is coded to Syria), or responses containing a geographic qualifier such as east or west (for example, South of England is coded to England).

Responses which relate directly to a country category but which consist of alternative spellings (for example, Tadzhikistan for Tajikistan), abbreviations (for example, Aust. for Australia), acronyms (for example, US for United States of America), or foreign language names (for example, Ceska Republika for the Czech Republic) are allocated the code of that country category. Similarly, slang or idiosyncratic responses (for example, Aussie or Oz for Australia) are allocated the code of the country category to which they directly relate.

If a response consists of an archaic or historical name (for example, Persia for Iran) it is necessary to determine the current country or geographic area to which the response relates and allocate the appropriate code: country; minor group, nfd; major group, nfd; or Inadequately Described. It should be noted that special supplementary codes have been assigned to the recently defunct political entities of eastern Europe (former USSR, former Czechoslovakia, etc.) and these codes should be used rather than the standard supplementary codes.

Responses which cannot be identified as relating directly to a separately identified country in the classification are assigned a residual category code or a supplementary nfd code as described above (see Reserved codes for residual categories, and Supplementary codes). Responses which do not contain sufficient information to be coded to any category of the classification are assigned the appropriate inadequately described code.

Changes in national boundaries create coding difficulties. In order to maintain consistency of coding in all applications it is preferable that each country response be coded according to national boundaries existing at the time of the data collection. Therefore, all responses relating to a country which currently exists, but which has undergone boundary changes at some time in the past, are coded to the named country. For example, all persons who give their country of birth as 'Poland' are coded to Poland, even though the boundaries of Poland may have changed since they were born and they may have in fact been born in a place that is now in Germany. Birthplace responses which relate to particular cities or regions which are now in one country, but which may have been in another country at the time of birth, should be coded to the country the city or region is in at the time of collection of the data. For example, the response 'Danzig' should be coded to Poland not to Germany and it is included as such in the coding index.

Responses relating to countries which have changed name, without changing boundaries, are coded to the latest name in the classification. Thus the response 'Upper Volta' is coded to 'Burkina Faso'.