Self defined ethnicity

Self defined ethnicity 'codes' are a set of codes used by the Home Office in the United Kingdom to classify an individual's ethnicity according to that person's self-definition.

Codes

The codes are also called "18 + 1" codes, as there are 18 of them, plus one code for "not stated". In addition to the previously used 16+1 codes, they contain the categories W3 and O2, while A4 is now replacing O1.
The code system originated in the 2001 [United Kingdom census] based on Recommendation 61 of the Stephen Lawrence Inquiry Report (SLIR).
British police forces are required to use the SDE 18+1 codes when spoken contact has taken place and an individual has been given an opportunity to state their self-perceived ethnicity.

List of SDE codes

;WhiteW1 - BritishW2 - IrishW3 - Gypsy or Irish TravellerW9 - White (classification of ethnicity in [the United">White (people)">White (classification of ethnicity in [the United Kingdom)|Any other White background]
;Mixed or Multiple ethnic groupsM1 - White and Black CaribbeanM2 - White and Black AfricanM3 - White and AsianM9 - Any other Mixed or Multiple background
;Asian or Asian BritishA1 - IndianA2 - PakistaniA3 - BangladeshiA4 - ChineseA9 - Any other Asian background
;Black, Black British, Caribbean or AfricanB1 - CaribbeanB2 - AfricanB9 - Any other Black, Black British or Caribbean background
;Other ethnic groupsO2 - ArabO9 - Any other ethnic group
;Not statedNS - Not Stated.