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Occupational coding in practice: from the

1981 to 2001 Census of Population

Tessa Staples

June 2004

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Census Occupational Coding 1981 to 2001

Transition

1981 Manual or Clerical coding

- 10% Sample

1991 Computer assisted coding

- 10% sample

2001 Automated coding(automatic coding and interactive

coding)

- No sample processing

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Census Occupational Coding 1981 to 2001

Census processing

1981 Managed in-house

- Titchfield and Bootle offices

1991 Managed in-house

- Titchfield and Hillington offices

2001 Contracted to Lockheed Martin

- Widnes office

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Census Occupational Coding 1981 to 2001

Classifications and coding frames1981 Classification of Occupations 1980

351 operational codes

1991 Standard Occupational Classification (1990)

480 component codes

2001 Standard Occupational Classification 2000

353 unit group codes

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Census Occupational Coding 1981 to 2001

Information needed by the coding index

CO80 SOCSOC

1990 2000

Job title Job description

Industry of employer

Professional qualifications Employee/Self-employed Major organisation

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Census Occupational Coding 1981 to 2001

Occupation coding index

Principles and layout style were devised

for efficient clerical coding• Simple look-up• Quicker coding• Greater coding consistency

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Census Occupational Coding 1981 to 2001

Occupation coding index

Using indexing words

Warehouse manager

Warehouse salesman

Warehouse cleaner

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Census Occupational Coding 1981 to 2001

Occupation coding index

Using indexing words

Warehouse manager = 1162

Warehouse salesman = 7111

Warehouse cleaner = 9233

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Know your onions - at the check-out

“Why can’t I find onion in the list?”

Census Occupational Coding 1981 to 2001

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Know your onions - at the check-out

Because listed as

‘Brown onion’

Census Occupational Coding 1981 to 2001

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Census Occupational Coding 1981 to 2001

Occupation coding index

Reverse word order

In response - Pest control inspector

In index - Inspector, control, pest

• Brings together variations on the indexing word in one place

• Enables use of ‘default’ entries

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Census Occupational Coding 1981 to 2001

Occupation coding index

Qualifiers to indexing words

• Occupation qualifiers• Additional qualifiers • Industry qualifiers

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Census Occupational Coding 1981 to 2001

Occupation coding index

List for Gateman

8219 Gateman, bridge

8219 Gateman, dock

8219 Gateman, flood

8219 Gateman, lock

8216 Gateman (coal mine)

8219 Gateman (docks)

9249 Gateman (entertainment)

8216 Gateman (railways)

8219 Gateman (waterways)

9241 Gateman

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Census Occupational Coding 1981 to 2001

Occupation coding index

List for Chain makers

5495 Maker, chain (metal, precious)

8129 Maker, chain (metal)

5211 Maker, chain (metal trades, forging)

8129 Maker, chain (metal trades)

8113 Maker, chain (textile mfr)

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Census Occupational Coding 1981 to 2001

Occupation coding index

Power of the default entries

(from use of index in 1991 Census)

Cleaner 35.9%

Cleaner, school 8.0%

Cleaner, office 6.4%

Cleaner, window 6.0%

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Census Occupational Coding 1981 to 2001

Organisation - 1981 and 1991 CensusesHeadquarters

• Instructions, coding indexes (amendments), training exercises

• Analysis of coding queries

• Independent quality control - ‘blind’ checking

• Audit inspection - 1991 only

Teams coding occupation and employment status

• Supervisors - answered coding queries

• Coders

• Query writers - 1991 only

• Query resolvers - 1991 only

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Census Occupational Coding 1981 to 2001

Organisation - 2001Census

Headquarters - ONS • Guidance, master copy of coding index (amendments),

tuning data (thousands of coded job titles in natural word order)

• ‘Second stop’ query resolvers• Sight checking

Teams coding occupation (some cross-topic training)

• Supervisors • Frontline coders• Expert coders - ‘First stop’ query resolvers

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Census Occupational Coding 1981 to 2001

1981 Census coding

Coders used• Census specific coding instructions

– also on an A3 sized flowchart• Modified Occupation Coding Index

– notes on coding– most industry qualifiers converted to

Census industry codes

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Census Occupational Coding 1981 to 2001

1981 Census Modified Occupation Coding IndexGateman;

bridge … … … … … 338

dock … … … … … 338

flood … … … … … 338

lock … … … … … 338

Gateman- … … … … … 140

503 … … … … … 321

742 … … … … … 321

746, 749 -

waterways .. … … … 338

750 … … … … ... 338

801,802 … … … … 165

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Census Occupational Coding 1981 to 2001

1991 Census coding

Coders used• Census specific coding instructions

– also on an A3 sized flowchart• ‘Computer Assisted Census Occupation

Coding’ (CACOC)– displayed the modified occupation

coding index on the screen of a stand-alone PC

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Census Occupational Coding 1981 to 2001

1991 Census coding

CACOC• developed by Census IT staff at General

Register Office for Scotland (GROS)• similar to the Australian coding tool, ASCO• not to reduce the number of coders but

achieve better coding consistency (?)

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Census Occupational Coding 1981 to 2001

1991 Census - CACOCOCCUPATION TITLE: GATEMANGateman

bridgedockfloodlock503742746,749

waterways750801,802Except above

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Census Occupational Coding 1981 to 2001

1991 Census - CACOCOCCUPATION TITLE: GATEMANGateman

bridgedockfloodlock503742746,749

waterways750801,802Except above

420

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Census Occupational Coding 1981 to 2001

2001 Census• Capture and coding contracted to

Lockheed Martin• LM chose ACTR (Automated Coding by

Text Recognition) as the coding tool• ONS’s Census staff specified contract and

provided much support to LM• Processing operation subcontracted to ICL• ICL’s Knowledge Pool produced the

training material

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Census Occupational Coding 1981 to 2001

2001 Census - Occupation coding screen

Image of census form Job title on record

Qualifications indicator box

Code Unit group title

Choice list

Accept

Industry code SIC group title

Not codeable To expert

Enter text for search

Search

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2001 Census - Occupation Coding Job title on record = Cellzzman

Industry code on record = 51

Text entered by coder = CELLARMAN wineSOC SIC Text

9149 159 Cellarman <wine mfr.>

9149 51 Cellarman <wine merchants>

8111 159 Cellarman

9225 551 Cellarman

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9225 BAR CELLARMAN

9225 BAR/CELLAR SUPERVISOR

9225 BAR STAFF/CELLARPERSON

Census Occupational Coding 1981 to 2001

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Number of occupation coding queries

1981 - 37,000 Apparently too few

1991 - 175,000 (in 54 metal trays on three trolleys)

2001 - 33,000 As sent to ONS

Revising the coding index during processing 1981 1991

2001

Number of times the index was revised 6 4 10

Total number of changes 131 393 311

Census Occupational Coding 1981 to 2001

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Independent quality control reported

1981 Census - 4.9% error rate

1991 Census - 5.5% error rate

2001 Census• Contract specified as acceptable

12.0% error rate• Lockheed Martin reported

8.9% error rate• ONS assessed from sight checking

10.96% error rate

• Automatic coding throughput

72.2%

Census Occupational Coding 1981 to 2001