A 2001 Census Area Statistic (CAS) sector was one of 2 special postcode sectors created for 2001 Census Output.
A postcode sector comprises all the unit postcodes that have the same identifier except for the last two characters. Special postcode sectors are created for census output to ensure sectors conform to a minimum threshold and do not cross Council Area boundaries. CAS sectors have a minimum threshold of 20 households and 50 persons, the same minimum threshold as Census Output Areas. There are 1,010 CAS sectors.
