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Census Learning Zone

Why Use Postcodes?

Scotland has approximately 138,000 Royal Mail postcodes. Each code refers to about 16 individual addresses. Postcodes apply to homes, offices, shops and factories on the mainland and on every populated island with the exception of St Kilda. They are used to ensure the mail is delivered quickly and correctly. Everyone knows their own postcode. This is why postcodes have formed such an important element of the Census organisation for the past 25 years.

Because new houses are built and new addresses are created the General Register Office uses Frozen Postcodes. All postcodes, which exist up to the December before a Census, are called frozen postcodes and are used in the Census. Any postcode collected in enumeration that does not belong to this set is replaced during processing by the most appropriate frozen postcode.

The General Register Office for Scotland, which carries out the Census, has created a computer system which links the postcodes to larger administration areas, such as your local Council or Ward.

When the time for a Census comes round - every 10 years - the Census Data Collection team use the postcodes to make up maps and lists of addresses in what are called Enumeration Districts. In this way every Enumerator who has to go round and deliver forms ends up with no more than approximately 400 addresses to visit.

Some Enumeration Districts are very large because they are in rural areas where people live in homes that are far apart. Some Districts are very small because the 400 addresses are all contained within several high-rise blocks of flats.

Every one of the 7,000 Enumerators gets a list of addresses and a large-scale map individually created for their particular area. So the postcodes are used, with the help of a computer, to give all the Enumerators about the same amount of work to do.

When all the millions of forms are returned, and after the information is scanned and recorded, the statisticians get to work to produce the thousands of tables which give a detailed picture of the people of Scotland. At this stage the postcodes are used again to group the information into Output Areas from which the users - regional councils, health boards, the government, and businesses - can extract all the details they need.

The postcodes are also used to make sure no individual person can be identified by grouping Census form information together in a way which ensures complete secrecy for everyone.

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