Family Resources Survey 2000-01
GSS Harmonisation Project
In 1995, a number of Government Departments came together to discuss the best way of making the results of major official surveys comparable. This led to the Harmonisation Project, whereby the inputs - the questions and related interviewer instructions and edit checks - used in the major surveys, and outputs - the concepts for analysis and publication - from them, is identical in as many of the surveys as possible. A list of the current harmonised questions may be found at http://www.statistics.gov.uk/harmony/introduction.asp.
Different surveys have different purposes and hence cover topics in different depths. Harmonised questions are designed to provide the recommended minimum information to allow common classifications and facilitate the analysis of data from different surveys in combination. Not all surveys will include questions on all topics or in every year, but the recommendation is that, where a topic is covered, harmonised questions should be included wherever possible.
Some surveys will require further detail on topics than can be obtained from the harmonised questions alone. It will normally be the case that such surveys already ask for that detail. The harmonised questions have been designed so that the surveys which ask for more detail can either derive them, without asking them directly, or combine them with the further detail, without adding to the length of interview. The FRS has actually set the standard for a number of harmonised questions, but many more on the FRS are being changed to fall in line with government surveys such as the Survey of English Housing, the Expenditure and Food Survey and the Labour Force Survey.
Harmonisation on the FRS covers:
- accommodation and tenure;
- age and gender;
- consumer durables;
- economic activity and length of time since last in paid work;
- educational attainment;
- ethnic origin and national identity;
- geographical classifications;
- household insurance;
- household reference person and household response unit;
- housing costs and benefits;
- industry, occupational and socio-economic classifications;
- legal marital status and living arrangements;
- length of residence;
- reference period;
- social security benefits and tax credits;
- time in present job and usual hours in present job;
- and vehicle ownership;
An area where the FRS output categories differ from harmonisation proposals is disability. The harmonised question for dealing with the hetitleh of individuals is:
Do you have any long-standing illness, disability or infirmity? By long-standing I mean anything that has troubled you over a period of time or that is likely to affect you over a period of time?
On the FRS, individuals who answer 'yes' to this question are also asked if this illness or disability limits their activities in any way and if they are registered disabled. In addition all adults below pension age are asked if they are restricted in the work they can do by some illness, injury or disability. Responses to all these questions are used to define sick or disabled adults for use in the household composition and economic status classifications (ILO definitions are based on those who have stated they cannot work or look for work because of sickness/disability).
Table M.7: shows hetitleh status by age group using the different definitions. As can be seen, the additional query about whether activities are limited by the illness or disability does affect the classification. The final column shows also that up to state retirement age there are some individuals who consider themselves restricted in the work they can do but have not categorised themselves as disabled.
Differences due to survey design features
Despite the use of harmonised inputs, there will inevitably be differences in the outputs of the varied surveys as a result of differences between the design of the surveys (and due to sampling variability). Primary among these is sample size; where the direct results of a survey are grossed up to estimate a total population, assumptions have to be made of the relevance of identified features to that population and it is reasonable to expect a wider margin of error from a sample of, say, 5,000 than from one of 50,000.
Relevant survey design features include:
- question wording and context effects;
- definition differences;
- non-response bias;
- geographical coverage;
- sampled population;
- mode effect;
- acceptance of proxy information;
- treatment of multi-households;
- unit of analysis;
- field practices;
- item non-response;
- time period;
- organisational effect.
Further details are provided in Amanda White and Sarah McCreith's 'An initial look at harmonised survey data', Survey Methodology Bulletin 43 (July 1998).
The GSS is continuing to try to quantify these likely differences, and advise users of official statistics of where such differences likely to arise, the reasons for them, and the potential size of any.
