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1 Background to the Survey

INTRODUCTION

The Scottish Household Survey ( SHS) is a continuous survey based on a sample of the general population in private residences in Scotland. The survey started in 1999 and is financed by the Scottish Government. Since 1999, the SHS was carried out by a team from Ipsos MORI and TNS System Three. 2007 marked the start of the latest four year contract, at the start of which the survey was revised and extended. Reflecting this, the research team was expanded to include the Scottish Centre for Social Research.

The SHS is designed to provide reliable and up-to-date information on the composition, characteristics and behaviour of Scottish households, both nationally and at a sub-national level. It covers a wide range of topics to allow links to be made between different policy areas. The specific aims of the survey are:

• To provide household and individual information particularly to support the work of the Scottish Government's transport, communities and local government policy areas and the work of the Scottish Parliament;
• To permit disaggregation of information both geographically and in terms of population sub-groups (such as families with children or the elderly);
• To allow the relationships between social variables within households to be examined. This will support cross-cutting analysis on a range of issues;
• To allow early detection of national trends;
• To allow detailed follow-up surveys of sub-samples from the main survey sample, if required.

CHANGES TO THE SHS IN 2007

A number of changes were made to the SHS at the start of the latest contract period. These included a revised sampling strategy, described below, which was designed to increase the efficiency of the survey; providing estimates with the same degree of precision from a reduced sample size. As a result of these revisions, data was collected from 13,414 householder interviews and 12,242 "random adult" interviews in 2007. The previous (2006) survey covered 15,618 households and 14,190 random adults.

The survey was extended to include a boost module designed to collect policy relevant information on culture and sport. The results of this module will be published in a separate report later in 2008. ¹ The existing questionnaire was reviewed prior to the start of 2007 and a number of sections were revised to maintain their policy relevance. In particular, the way information was collected about trips made the previous day in the Travel Diary was changed and shorter journeys of five minutes duration or less were included to enable data to be collected on an increased number of journeys.

Due to the high level of demand for space in the Scottish Household Survey, a number of sections of the questionnaire are asked of random sub-samples of the full SHS sample. This is achieved by randomly assigning addresses to one of ten sub-samples, referred to as 'streams', within the interview. Further streaming was undertaken in June 2007 to reduce the length of the questionnaire as it was longer than originally planned.

Two streams (1 and 6) are reserved for the Culture and Sport module. The remaining eight are used for the 'main' SHS script. Decisions on the number of streams in which particular questions appear are based on criteria including the expected size of a particular variable, and requirements for sub-analysis. Theoretically, the streaming design allows questions to be assigned to as little as one-eighth of the main sample. In practice, streamed questions were asked of at least one quarter of the full sample in 2007. In this report, where a specific question was asked of a reduced sample size, this is indicated in the relevant table. Where streaming took place only for part of the year, this is also indicated. Additional streaming will be achieved by asking some questions in two years during the four year contract period.

Full details of the changes to the questionnaire and of the interview streams can be found at www.scotland.gov.uk/shs.

SAMPLING

The sample for the survey meets a number of criteria. It is designed to provide nationally representative samples of private households and of the adult population in private households. This is achieved by splitting the interview between a household respondent and an adult selected at random from the permanent residents of the household.

In order to meet the reporting requirements, the sample is structured to be nationally representative each quarter and to provide a representative sample for larger local authorities each year. The sample is also designed to provide data for every local authority over a two-year period. ² This is achieved by disproportionately sampling to achieve a minimum sample equivalent to a simple random sample of 500 interviews in each local authority area. This report is based on data collected in 2007, the first year of a two year sampling period (2007/08).

The current sample design, like the one used from 1999 to 2006, uses a multi-stage stratified design with a mix of unclustered and clustered sampling. For 2007, the sampling strategy was revised to achieve a higher proportion of interviews from unclustered sample. In general, reducing the level of clustering in a sample increases its statistical efficiency, allowing the same level of precision to be achieved with fewer interviews than would be required from a clustered sample. However, unclustered sampling is generally more expensive, particularly in rural areas because of the larger distances between addresses. The revised sampling strategy was designed to achieve the optimum balance between these. As a result, the cost-effectiveness of the interviewing has improved compared with the previous design because it now requires fewer interviews to achieve the same level of precision.

The SHS sample is selected from the small user Postcode Address File ( PAF) for Scotland, expanded to take account of addresses which might only be listed once but actually contain multiple dwellings, such as tenement blocks and multi-storey flats. Although the small user PAF excludes many institutional addresses such as student halls of residence or nurses' homes, there are no geographical exclusions from the survey, which covers all parts of Scotland, including the Highlands and Islands.

The main features of the current design are:

• first stage, disproportionate stratification by local authority;
• within each local authority, second stage stratification by the Scottish Government's urban rural classification with large urban and other urban areas combined into an 'urban' stratum and all other areas combined into a 'rural' stratum;
• unclustered sampling is used in the 'urban' stratum, with addresses sorted by Scottish Index of Multiple Deprivation ( SIMD) and selected systematically from a random starting point;
• clustered sampling is used in the 'rural' stratum, with datazones used as primary sampling units which are selected with probability proportionate to size and, within each, a systematic sample selected from a random starting point.

There are some variations to this overall design:

• In local authorities with 80% or more of the household population in 'urban' areas, the sample is wholly unclustered;
• In local authorities with 80% or more of the household population in 'rural' areas, the sample is wholly clustered;
• The local authorities of Western Isles, Orkney and Shetland have wholly unclustered samples even though the urban rural classification suggests they should be wholly clustered. The reason for this is that sample size in these areas means that between 1 in 6 and 1 in 8 households should be sampled. Clustered samples in these areas would be no more efficient than an unclustered sample but would require larger samples for the same level of precision.

THE SHS INTERVIEW

Interviewing is conducted in respondents' homes using Computer Assisted Personal Interviewing ( CAPI). Data are collected by interviewers on handheld or laptop computers.

The survey questionnaire is in two parts. The household reference person, who is the highest income householder ( HIH) or their spouse/partner completes Part 1 of the interview. Details of all members of the household, including children, are collected during the household interview. Subsequently a child is selected from all household members under 16 (the 'random child') and the household respondent is asked questions about childcare for that child. A child who is at school is also selected ³ (the 'random school child') and the household respondent answers questions about the school the child attends and the journey they make to go there.

Once the composition of the household has been established, one of the adults in the household is randomly selected by the computer to complete Part 2. ⁴ In all households with a single adult the same person completes both parts, but as the number of adults in the household increases, the probability of the random adult being the same as the household respondent declines. ⁵

The household section of the interview deals with topics such as household composition and current economic situation of household members; accommodation, access to the internet and broadband connection; recycling; cars available to the household, employment details of the highest income householder; household income, savings and use of financial services; housing costs; childcare and schooling. The random adult section deals with marital status, ethnicity and religion, individuals' accommodation change; experiences of homelessness and housing problems; neighbourhoods and community safety; transport modes, car dependency, congestion and road safety; travel planning; use of the internet; public services; income and employment; participation in culture and sport.

RESPONSE RATES

After excluding addresses that were outwith the scope of the survey, ⁶ the overall response rate for this sweep was 65.6%. There was significant variation in response between local authorities. The highest response rate was achieved in Orkney (80.2%) and the lowest response was achieved in Glasgow (54.8%).

WEIGHTING

Post-survey weighting takes account of both the disproportionate sampling between local authorities and the differential response between authorities. The data presented in the report have been weighted in one of two ways. Household data (collected in Part 1 of the interview) are weighted to take account of the disproportionate sampling and response between local authorities. Random adult data (from Part 2) are weighted to reflect both the disproportionate sampling and response to Part 2 between local authorities and the different probabilities of selection within households. ⁷ Similarly, the data relating to the randomly-chosen schoolchild are weighted to reflect the disproportionate sampling and variation in response rates between local authorities and also the number of schoolchildren in the household. These weighted data have been compared with other official estimates and no additional weighting has been undertaken at this stage.

ADDITIONAL SHS REPORTING

Full details of the survey can be obtained from the companion Technical Reports. There are three parts to the technical reporting detailing separately the methodology, the fieldwork outcomes for 2007 and the questionnaire used. These can be found at www.scotland.gov.uk/shs.

A number of other Scottish Government publications covering previous years are also available. A comprehensive listing of all publications is available from the SHS website. ⁸

THE ANNUAL REPORT

SHS results have been reported in a series of 8 Annual Reports between 1999 and 2006. The Scottish Government's ambition during the current contract is for the SHS data to become even more widely used. A dissemination strategy has been produced following consultation with existing users which builds on the Review of the Survey carried out in 2005. The first part of the strategy is the extensive revision of the Annual Report. The revision has included cutting the number of tables, while at the same time providing extended commentary on those that remain. It has also been visually updated.

Changes have been made to the purpose, format and content of the report. It is designed to act as an introduction to the survey and to present and interpret some of the key policy-relevant results. Its previous parallel function as a reference tool for a fuller range of results has been replaced by the SHS website where a large number of pre-analysed tables, including those presented in previous annual reports and a range of results by local authority groupings, are available for 2007 results. ⁹ Reducing the number of tables presented in the report has allowed more interpretation of individual results. The number of figures presenting summary results in graph format has been increased, part of the measures designed to improve the visual appeal and accessibility of the results.

At the start of a chapter, introductory paragraphs draw on key policy documents to set the results that follow into the policy context for the topic it covers. In most of the chapters, the introduction draws on the Scottish Budget Spending Review 2007. ¹⁰This document highlights the Government's overall purpose of increasing sustainable economic growth, and five strategic objectives, which are designed to ensure the purpose is delivered. The objectives that are most relevant to the subject of a chapter, as defined in the spending review, are identified. The five objectives are:

Enable businesses and people to increase their wealth and more people to share fairly in that wealth;

Expand opportunities for people in Scotland to succeed from nurture through to lifelong learning, ensuring higher and more widely shared achievements;

Help people to sustain and improve their health, especially in disadvantaged communities, ensuring better, local and faster access to health care;

Help local communities to flourish, become stronger, safer places to live, offering improved opportunities and a better quality of life;

Improve Scotland's natural and built environment and the sustainable use and enjoyment of it.

Additional policy documents, such as more detailed strategies on particular policy areas, are drawn on as appropriate and are referenced in the text.

The SHS is the source of information on 5 of the 45 national indicators in the Government's National performance framework. ¹¹ One of the indicators ¹² is derived from information collected in the travel diary and will be reported later this year. This report provides estimates for the remaining four national indicators:

Improve people's perceptions of the quality of public services delivered ( Chapter 11);

Reduce the percentage of the adult population who smoke to 22% by 2010 ( Chapter 10);

Increase the percentage of adults who rate their neighbourhood as a good place to live ( Chapter 4);

Increase the proportion of journeys to work made by public or active transport ( Chapter 8).

In some cases the SHS is not the official source of statistics on a particular topic such as income, employment or housing. The interview collects information on these topics to select the data of particular groups for further analysis or for use as background variables when analysing other topics. The results are included in order to set the context for and aid interpretation of the remaining chapters. Where results are not the official source, this is indicated in the chapter introduction.

The results are presented in the remaining 12 chapters covering: household composition; housing; neighbourhoods and communities; economic activity; financial inclusion; education; transport; internet and broadband; health and caring; local services; volunteering; culture and sport. Guidance on using the information in the report and a glossary with detailed definitions of some of the key terms are included as annexes. Additional annexes present results on the main classificatory variables used in this report and provide guidance on assessing confidence intervals and the statistical significance of the results.

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