Sampling

The Population Sampled

The sample for data collection during 2021 was designed to be representative of the adult population aged 15+ of Great Britain. The survey population is estimated to be 53,927,883 according to JICPOPS mid 2021 projections based on 2011 census data. All details below relate to the sampling process for the 2021 survey.

Overview of the PAMCo Sample

PAMCo has a multi-stage disproportional pre-selected sample design.

The three stages of sampling are as follows:

Selection of sampling points
Selection of addresses
Selection of individuals

The sampling frame for the selection of sampling points comprises all Output Areas (OAs) in Great Britain. Two OAs are selected per sampling point.

The sampling frame for the selection of addresses is the Postal Address File (PAF).

Data collection is divided into two stages, each with its own procedure for the selection of the household members to be sampled.

At an initial postal stage, three mailouts are sent by post to each address and any two household members aged 15+ are invited to complete the survey.

At the field stage Interviewers are issued with the addresses where there has been no survey completed (and no refusal to take part) at the postal stage. At each household contacted they enumerate eligible individuals aged 15+. The final stage of the sampling is then to select which of these eligible individuals should be interviewed. One individual is selected in most households, and up to two individuals in larger households. The rules as to how this is done are described later in this document.

Some disproportional sampling is used at the stage of selecting sampling points in order to over-sample certain ACORN areas particularly likely to contain individuals with AB social grades.

Selection of Sampling Points

The first stage of sampling is to select the sample points (or locations) where data collection will be carried out. Before this is done, certain ACORN areas are upweighted (and others downweighted). This is done so as to oversample areas where individuals with AB social grades are particularly likely to live, and therefore increase the number of interviews taken with AB participants.

The steps taken to select the sampling points are therefore as follows:

a) Sampling weights are applied to the adult populations of OAs by 7 categories of ACORN Types, as follows:

Category	ACORN Types	Weights Applied
1	1, 2, 3	1.91
2	4, 5, 7, 8, 9, 14, 16	1.63
3	6, 10, 15, 17, 61	1.36
4	11, 12, 13, 18, 19, 20, 21, 22, 24, 26, 32, 62, 00	1.11
5	23, 25, 28, 29, 31, 33, 34, 37, 53, 54, 60	1.01
6	27, 30, 36, 38, 41, 49, 50	0.74
7	35, 39, 40, 42, 43, 44, 45, 46, 47, 48, 51, 52, 55, 56, 57, 58, 59	0.65

b) Great Britain is divided into 60 area groupings, devised for PAMCo, individually weighted and used to piece together the Government Office Region and non-overlap ISBA TV regions.

A full list of the 60 areas can be found overleaf. For the purposes of sampling, the area groupings are further sub-divided into district groupings.

c) The weighted adult populations of each of the 60 area groupings are calculated. The target number of sampling points for each area grouping is then set. The total number of points at this stage is 1,616 per annum.

d) Within each area grouping, OAs are ranked in descending order by PAMCo district grouping, then within district by PAMCo ACORN category, and finally within PAMCo ACORN category by NS-SEC.

e) The required number of OAs within each area grouping as specified at b) is then selected with probability proportional to weighted adult populations, using random start/fixed sampling interval procedures.

f) Any selected OA falling into a ‘no-go’ area (as separately defined) is replaced with one in the sample District and same ACORN Type with population size closest to the originally selected OA.

g) Modified procedures are applied in Scotland in areas 49, 50, 51, 52, 56, 57, 58 and 59. In these areas the target number of points is increased, relative to other areas, to the numbers shown in the table overleaf.

Sampling Areas

The area groupings used and the target number of Sampling Points selected for data collection in 2021 are as follows:

England and Wales

Area Groupings	Government Office Region	ISBA Area	No. of Points Selected
1	South West	South West	44
2	South West	Southern	24
3	South East	Southern	40
4	South East	Southern	20
5	South East	Southern	28
6	South East	Southern	52
7	South East	London	40
8	East of England	London	56
9	Greater London	London	36
10	Greater London	London	72
11	Greater London	London	48
12	Greater London	London	52
13	East of England	East of England	36
14	East Midlands	East of England	16
15	South East	London	24
16	East of England	East of England	24
17	East of England	East of England	36
18	South East	Midlands	28
19	South West	Midlands	16
20	West Midlands	Midlands	44
21	West Midlands	Midlands	28
22	Greater London	London	32
23	West Midlands	Midlands	16
24	West Midlands	Midlands	16
25	West Midlands	Midlands	28
26	East Midlands	Midlands	24
27	East Midlands	Midlands	20
28	East Midlands	Midlands	24
29	Wales	Wales and the West	8
30	Wales	Wales and the West	24
31	Wales	Wales and the West	28
32	North West	Border	12
33	South West	Wales and the West	20
34	South West	Wales and the West	36
35	Yorkshire and the Humber	Yorkshire	48
36	Yorkshire and the Humber	Yorkshire	28
37	Yorkshire and the Humber	Yorkshire	24
38	East Midlands	Yorkshire	28
39	Wales	Lancashire	8
40	North West	Lancashire	36
41	North West	Lancashire	36
42	North West	Lancashire	16
43	North West	Lancashire	28
44	North West	Lancashire	32
45	Yorkshire and the Humber	North East	16
46	North East	North East	28
47	North East	North East	12
48	North East	North East	12

Scotland

Area Groupings	Area Names	No. of Points Selected
49	Aberdeen	8
50	Dundee	8
51	Edinburgh	24
52	Strathclyde, urban	64
53	Strathclyde, rural	24
54	Lothian	12
55	Central	12
56	Fife	12
57	Other Tayside	12
58	Other Grampian	12
59	Highland	12
60	Scottish Borders	12

Allocation to Questionnaire Version

Each sampling point is assigned a code to determine the rotation order to be used to ask about the various newspapers and magazines during that particular assignment. For details of the rotation orders, see document entitled ‘The Interview’.

Selection of Addresses

Within each selected pair of OAs, 32 or 33 addresses are selected, apart from London where 35 addresses are selected.

At the field stage, addresses are issued to the interviewer via the Electronic Contact Sheet (ECS) software on their tablet computer.

A minimum of three calls is prescribed for each potentially productive address, of which at least one at the weekend and one on a weekday evening, before attempts to interview can be abandoned. Interviewers are encouraged to make as many calls as possible, varying them by time of day.

Selection of Individuals

The selection of individuals is done within the ECS using the following steps:

a) All selected addresses within each selected OA are allocated the letters P, Q, R and S consecutively.
b) For all issued addresses the ECS specifies the one or two persons to be interviewed, as follows:

Address Letter

No. of adults at address	P	Q	R	S
1	First	First	First	First
2	First	Second	First	Second
3	Second	First, Third	Second, Third	First
4	First, Fourth	Second, Third	First, Fourth	Second, Third
5	Second, Fourth	First, Fifth	First, Third	Second, Fifth
6+	First, Youngest	Third, Fifth	Second, Fifth	Fourth, Youngest

The ECS instructs interviewers to list all persons aged 15+ in a selected household, in descending order of age, and then confirms the person(s) selected for interview, depending on the total number of adults at the address and the letter allocated to that address.