Update on the development of the Integrated Household Survey

Nikki Bennett & Leicha Rickards Office For National Statistics

Overview

• Key aims • Key design features• IHS dependencies• Phased IHS implementation • Questionnaire content and design• Sample design• Weighting and output strategies• Continuity management• Implementation timetable

IHS: key aims (1)

To develop an integrated household survey that will:

– deliver a range of better quality, more reliable estimates at national, regional and particularly, sub-regional levels

– produce a range of new, regular outputs from a very large dataset of core information

– improve coherence in official statistics through fewer competing survey estimates

– deliver efficiencies through standardisation, integration, modernisation and better design

IHS: key aims (2)

• Greater harmonisation of concepts, classifications, questions and outputs

• Increased flexibility to sample respondents to produce estimates to required level of precision

• Better sample coverage at local authority district level through reorganisation of sample and fieldwork

• More responsive and flexible in meeting new needs – can add topic modules or new interview combination – much cheaper than a new survey

Which surveys?

• Labour Force Survey (LFS)– including annual sample boosts

• Longitudinal General Household Survey (GSL)• Expenditure & Food Survey (EFS)• Omnibus Survey (OMN)• English Housing Survey (EHS) – merged SEH and

EHCS for CLG

• Scope for other surveys to be integrated using the IHS design & data collection infrastructure

– subject to fieldwork capacity, design requirements and customer funding

IHS: key design features

• Integrated and unclustered sample and fieldwork design

– existing GSL, OMN, EFS and EHCS have clustered design

• Modular questionnaire design– core set of key socio-demographic information collected

from all responding households (core module) – topic modules of questions collected from sub-sets of

the sample (topic modules)– core and topic modules combined to create a number of

different interview types

IHS: key dependencies

• A single integrated field force of interviewers able to administer all types of interview combinations in small geographical areas

• An enhanced survey case management system to increase our ability to manage field operations effectively and efficiently

Survey case management system

• Delay to project delivering the new survey case management system (SCMS)

• Integrated and unclustered sample and fieldwork design is dependent on the new SCMS being in place to support more complex data collection operation in the field

• Need to conduct large field operational test with both integrated fieldforce & SCMS in place ahead of unclustering the IHS sample

• This impacts on when unclustered design can be implemented

Phased implementation of the IHS during 2008

Jan 2008 •New core module of questions to be added to GSL, EFS and Omnibus questionnaires

Apr 2008 •New core module of questions to be added to the LFS and new EHS•New survey case management system to be launched

Oct 2008 •Unclustered sample design

IHS: sample design (1)

• Overall design closely mirrors that of the existing combined QLFS and annual LFS boost

• Single unclustered sample of new addresses, stratified by UA/LAD (i.e. more finely than the current UA/LEA)

• Cases then assigned to interview/sample types.

• Only carrying forward LFS requirement for communal establishment coverage for 2008

– may extend this in some parts of the survey in future (subject to demand and funding)

• The sample will include a number of panels, as well as single interviews

IHS: sample design (2)

• Approx. 221,000 household interviews will be available for the annual dataset of core information

Interview Type Set sample Household interviews

‘GHS’ type 22,000 10,000

‘EFS’ type 11,500 5,700

‘Omnibus’ type 24,000 16,000

‘QLFS’ type 255,000 216,000

‘Annual LFS’ boost 130,000 88,000

EHS 29,100 17,300

Annual total 471,600 353,000

•The expected breakdown of the annual sample by interview types is as follows

IHS: Core (1)

• Core set of information from each household – Household, family and individual level variables– Fixed core questions (each year)– Rotating core (every few years – subject to demand and funding)

• Criteria for consideration for inclusion in core– Classificatory variable essential for analysis– Clear requirement for a high level of precision nationally, regionally

or sub-regionally and not provided elsewhere – Information that can be collected either face-to-face or by telephone

interview– Proxy responses acceptable– Topics which would not adversely affect response to the interview

as a whole– Stability of funding over time

IHS: Core (2)

• Common concepts and question wording but not a strict adherence to a common core module of questions at the start of each interview

– due to concerns about interview flow

– need to return to topics

– context and order (based on evidence from early field trials)

• Some topic-specific questions will be interwoven with core questions

– to improve flow

– reduce interview length

– minimises potential for discontinuities in key time series

• Trade-off between ideal and more pragmatic solution – no easy answer

IHS: Core (3)

• Core content to be confirmed via Steering Group

– now likely to be May

• Working closely with NS Harmonisation Working Group

• Ongoing collaboration with Census

– e.g. content, definitions, priorities, gaps

• Ongoing consideration of new requirements

– e.g. migration, sexual identity, household remittance

IHS: Core topicsDemographic:

Sex, age, marital status (inc. civil partnerships), living arrangements

Household type and composition: householder, relationships

Housing: Tenure, type of landlord, accommodation type

Identity and migration:

Ethnicity, religion, national identity, country of birth, year of entry to UK, length of residence, residence one year ago

Employment:

Economic & employment status, occupation and industry, job description, full-time/part-time

Income: banded gross household income (equivalised quintile groups), individual gross income

Family type & composition

Health:

General health (5-point scale), long-term and limiting longstanding illness, smoking

NS-SEC Education: Educational status, whether has any qualifications, age finished full-time education

IHS: Weighting (1)

• A number of different sets of weights will be needed on the IHS

– monthly, quarterly and annual weights and weights for longitudinal data.

• Two-phase weighting proposed for GSL and EFS modules.

– potential to produce worthwhile precision gains in survey variables as well as improving consistency on selected core variables.

• Two-phase weighting would not be used on the rolling-quarterly LFS files

– The case for two-phase weighting for the annual labour market data is not so strong in terms of precision gain but would improve consistency at an aggregate geographical level (probably GORs).

IHS: Weighting (2)

• All two-phase weighting controls would be applied at the regional level.

• On the GSL and EFS data (annual) household controls would be applied to achieve near-consistency (with residual inconsistency being caused by missing data) for:

– Tenure,

– Household type,

– NS-sec of the HRP,

– Economic status of the HRP,

– Ethnic group of the HRP,

– Count of employed/unemployed adults in the household

IHS: Weighting (3)

• If two-phase weighting method is applied to the rolling annual labour market household file, we will use these controls.

• If applied to the person file, we will need to use person-level controls.

• The set should include NS-sec, Economic status and Ethnic group and might also include other LFS-relevant variables such as economic status by sex, economic status by age group and full/part time for employees.

IHS: Outputs (1)

• Continue to deliver range of topic-specific outputs currently produced on existing LFS, GSL, EFS and Omnibus surveys (monthly, quarterly and annual)

• GSL and EFS annual datasets for calendar year 2008 will be based on data from a combination of clustered (Jan-Sept) and unclustered (Oct-Dec) sample designs

• New set of rolling annual outputs from the IHS whole sample core module and some precision gains on existing annual outputs

• First rolling IHS core outputs will be based on data collected from April 2008-March 2009 data and refreshed each quarter thereafter, July 2008-June 2009 etc..

IHS: Outputs (2)

• Annual datasets of core module data via UKDA and direct to customers – updated each quarter;

• aggregate core tables via NS Website – updated each quarter

• input data for small area estimation within ONS (subject to resources and funding)

IHS: Outputs (3)

• LAD/UA level rolling annual outputs updated each quarter (similar to APS outputs) but with a larger sample and wider range of topics, e.g

• Health

– % with Fair/Bad/Very Bad general health

– % with/without a longstanding illness by sex

– % with/without a limiting longstanding illness

• Family– % of households - married/cohabiting with children– % of households - married/cohabiting without children– % of households - other types of households– % lone-parent households– % of persons living alone

IHS: Outputs (4)

• Proposal for three types of microdata:

– Detailed but anonymous dataset to GSS users with low levels of geography;

– As above, but to trusted users, outside GSS, via UKDA under Special Licence.

• Proposed that this will have UA/LA codes connected to dataset and will provide richer source of data than existing annual local area LFS data

– A non-disclosive public dataset for release via UKDA.

• No geography below GOR level.

• Release of public data to coincide with release of tabular data on NS website and NOMIS

IHS Preparation: 2nd fieldwork pilot in Summer 2007

• Key features of the pilot– Set sample size of 3,375 addresses across ALL the IHS

interview types– Fieldwork in June and July 2007– Follow-up wave 1 LFS type interview in Sep/Oct 2007

(est. 1,200 addresses)– A mix of full-time, part-time and new interviewers (face-

to-face and telephone unit interviewers)– Test of integrated questionnaires and new training

techniques– Provides data important for understanding the impact of

IHS on current time series

IHS: Continuity management

• Continuity of key time series is important consideration in making the switch to IHS

• No longer proposing a full parallel run

– Not possible to manage this without introducing additional discontinuities which we could not quantify or distinguish from the potential change we were trying to measure.

– Even if practicable, only relatively large discontinuities could be measured using such an approach.

• Now proposing a "modelling" approach

– minimise the changes being introduced

– research the likely impact of changes, monitor the results of those changes

– use time series modelling to assess any residual discontinuity

IHS: implementation planMarch 2007 Finalise IHS 2008 core topics/questionnaires

June/July 2007 Conduct pilot fieldwork (Wave 2 test in Sept/Oct 2007)

January 2008 Introduce IHS core questions onto EFS, GSL & Omnibus. Clustered sample designs as now

April 2008 Introduce IHS core questions onto LFS & boosts and new EHS. Unclustered sample designs

April 2008 Use new survey case management system to support all household survey fieldwork

June 2008 IHS Dress Rehearsal

October 2008 Introduce new unclustered sample and fieldwork design

Continuity management work will be ongoing throughout

Thank you

Topics that may be on the Census but unlikely to be in the IHS core

• Visitors staying in the household• Number of rooms• Central heating• Number of cars/vans• Term-time address for students• Languages - English/Other/Sign• Frequency of use of Welsh• Second residence (including type, time spent

there)