Occupational coding:principles, practice and problems

A workshop within the ESRC Research Methods Programme

Peter EliasInstitute for Employment Research

University of Warwick

Royal Statistical Society, London June 2004

Principles of occupational coding

Aim:

to categorise an occupational description within an occupational classification

Rationale:

to reduce a complex set of information to a manageable set of categories which reflect the conceptual basis of the classification

Some definitions

What is the unit to be classified?A ‘job’ – a set of tasks/duties executed, or designed to be executed, by one person

What is an occupational description?Account of the main tasks and duties performed in a set of jobs which are characterised by a high degree of similarity

What do we mean by ‘similarity’?

Similar in terms of the underlying conceptual basis of the classification

What is the ‘conceptual basis’

This relates to the purpose for which the classification is designed (e.g. to measure ‘skill’, social positions, safety of the work environment, etc.)

Some definitions (contd.)

What is an occupational classification?

A set of categories which reflect the conceptual basis of the classification and within which all units can be appropriately classified

Usually described via a Structure, an Index and a set of Rules

Some definitions (contd.)

Coding practice

Self classificationPresent the informant with a set of occupational categories – they select most appropriate for the occupation they wish to classify

‘Coder’ classificationAll the requisite information is passed to a ‘coder’. Coding is achieved by comparing occupational information with the index to the classification, applying the coding rules to obtain the most appropriate code for the occupational category

Self-classification

Consistent coding requires all informants to have the same understanding of the nature of the classification (or, at least, for errors in coding to be normally distributed)

SOC2000 Major groups

1   Managers and senior officials2   Professional occupations3   Associate professional and technical occupations4   Administrative and secretarial occupations5   Skilled trades occupations6   Personal service occupations7   Sales and customer service occupations8   Process, plant and machine operatives9   Elementary occupations

Can you classify your job to SOC2000?

‘Coder’ classificationCollect required information:

Labour Force SurveyWhat was your (main) job (in the week ending Sunday [date])? <Interviewer Instruction - ENTER JOB TITLE>What did you mainly do in your job?<Interviewer Instructions - CHECK SPECIAL QUALIFICATIONS/TRAINING

NEEDED TO DO THE JOB>

Millennium Cohort (First survey)What is your (main) job? <Text: up to 40 characters>What do you mainly do in your job?<Interviewer: CHECK SPECIAL QUALIFICATIONS/TRAINING NEEDED TO

DO THE JOB<Text: up to 40 characters>

Compare information collected with index and apply coding rules

- reverse word order?

- default coding rules?- ‘see notes’?

- obtain code

‘Coder’ classification (contd.)

What problems can arise?

• Cannot always collect the information needed for detailed and accurate coding

• The index and/or the rules may not yield an appropriate code

• The process is complex, tedious and error prone

How do we resolve these problems?

• Give explicit instructions to informant, with examples

• Ask the right questions

• Update the index and the rules on a regular basis in the light of experience

• Coder training

• Interviewer coding

• Update the classification

Updating the Classification

1980 1990 2000

Classification of Occupations 1980 (CO80)

1990 Standard Occupational Classification (SOC90)

2000 Standard Occupational Classification (SOC2000)

CODOT and the Key list of Occupations for Statistical Purposes (KOS)

HE First destination statistics (SOC(FDS))

HE Destination of Leavers Survey (SOC(DLHE))

The classification of ICT occupations (1946-1972)

ED526 (1946-72)

Systems analyst/programmer (computers)

Programmer (computers)

Hollerith machine operator

CODOT (1973-90)

Office manager (records)

Data processing manager

Systems analyst

Computer programmer

Data processing machine operator

Computer operator

Sorting machine operator

Key punch operator

The classification of ICT occupations (1973-1990)

SOC90 (1991 – 2000)

Computer systems and data processing managers

Software engineers

Computer analysts/programmers

Filing, computer and records clerks

Typists and word processor operators

Computer and data processing machine operators

Computer engineers; installation and maintenance

The classification of ICT occupations (1991-2000)

SOC2000 (2001 – 2010)

ICT managers

IT strategy and planning professionals

Software engineers

IT operations technicians

IT user support technicians

Database assistants/clerks

Computer engineers; installation and maintenance

The classification of ICT occupations (2001-2010)

How well can we monitor occupational change?

• Monitoring trends requires that we ‘backcast’ occupational data when a new classification is introduced

• Different approaches to this:- recoding historical data (expensive)- use of ‘converter matrices’ (inaccurate)- preserving text descriptions for future reprocessing

Classification converters?

• LFS Winter 96/97 and Spring 2000 dual coded – SOC90 and SOC2000

• ’91 Census (E&W ½ % sample) ‘component coded’ – CO80 and SOC90

• 1990 New Earning Survey – KOS and SOC90

• For assistance, contact Occupation Information Unit

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

Info &communication

technologymanagers

IT strategy andplanning

professionals

Softwareprofessionals

IT operationstechnicians

IT user supporttechnicians

Databaseassistants &

clerks

Computerengineers,

installation &maintenance

Call centreagents &operators

19911996/72003

Growth of ICT-related occupations, England and Wales 1991- 2003

Good coding practice

• Code to the most recent version of the UK national occupational classification

• Adopt the wording of questions as developed by the Office for national statistics

• Create electronic records of text descriptions

• Train coders: promote understanding of conceptual basis of classification, nature of rules, use of index

• Where possible, dual code to previous occupational classification

• Conduct consistency checks