Labour Force Survey Five-Quarter Longitudinal Dataset, April 2021 - June 2022

<p><b>Background</b><br> The <i>Labour Force Survey</i> (LFS) is a unique source of information using international definitions of employment and unemployment and economic inactivity, together with a wide range of related topics such as occupation, training, hours of work and personal characteristics of household members aged 16 years and over. It is used to inform social, economic and employment policy. The LFS was first conducted biennially from 1973-1983. Between 1984 and 1991 the survey was carried out annually and consisted of a quarterly survey conducted throughout the year and a 'boost' survey in the spring quarter (data were then collected seasonally). From 1992 quarterly data were made available, with a quarterly sample size approximately equivalent to that of the previous annual data. The survey then became known as the <i>Quarterly Labour Force Survey</i> (QLFS). From December 1994, data gathering for Northern Ireland moved to a full quarterly cycle to match the rest of the country, so the QLFS then covered the whole of the UK (though some additional annual Northern Ireland LFS datasets are also held at the UK Data Archive). Further information on the background to the QLFS may be found in the documentation.<br> <br> <b>Longitudinal data</b><br> The LFS retains each sample household for five consecutive quarters, with a fifth of the sample replaced each quarter. The main survey was designed to produce cross-sectional data, but the data on each individual have now been linked together to provide longitudinal information. The longitudinal data comprise two types of linked datasets, created using the weighting method to adjust for non-response bias. The two-quarter datasets link data from two consecutive waves, while the five-quarter datasets link across a whole year (for example January 2010 to March 2011 inclusive) and contain data from all five waves. A full series of longitudinal data has been produced, going back to winter 1992. Linking together records to create a longitudinal dimension can, for example, provide information on gross flows over time between different labour force categories (employed, unemployed and economically inactive). This will provide detail about people who have moved between the categories. Also, longitudinal information is useful in monitoring the effects of government policies and can be used to follow the subsequent activities and circumstances of people affected by specific policy initiatives, and to compare them with other groups in the population. There are however methodological problems which could distort the data resulting from this longitudinal linking. The ONS continues to research these issues and advises that the presentation of results should be carefully considered, and warnings should be included with outputs where necessary.<br><br> <b>LFS Documentation</b><br> The documentation available from the Archive to accompany LFS datasets largely consists of the latest version of each user guide volume alongside the appropriate questionnaire for the year concerned. However, volumes are updated periodically by ONS, so users are advised to check the latest documents on the ONS <a href="https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/methodologies/labourforcesurveyuserguidance" title="Labour Force Survey - User Guidance" target="_blank">Labour Force Survey - User Guidance</a> pages before commencing analysis. <b>This is especially important for users of older QLFS studies, where information and guidance in the user guide documents may have changed over time.</b><br></p><p><span style="font-weight: bold;">Occupation data for 2021 and 2022 data files</span><br></p><p>The ONS has identified an issue with the collection of some occupational data in 2021 and 2022 data files in a number of their surveys. While they estimate any impacts will be small overall, this will affect the accuracy of the breakdowns of some detailed (four-digit Standard Occupational Classification (SOC)) occupations, and data derived from them. Further information can be found in the ONS article published on 11 July 2023: <a title="Revision of miscoded occupational data in the ONS Labour Force Survey, UK: January 2021 to September 2022" href="https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/articles/revisionofmiscodedoccupationaldataintheonslabourforcesurveyuk/january2021toseptember2022" style="background-color: rgb(255, 255, 255);">Revision of miscoded occupational data in the ONS Labour Force Survey, UK: January 2021 to September 2022</a>.</p><p><span style="font-weight: bold;">2022 Weighting</span></p><p>The population totals used for the latest LFS estimates use projected growth rates from Real Time Information (RTI) data for UK, EU and non-EU populations based on 2021 patterns. The total population used for the LFS therefore does not take into account any changes in migration, birth rates, death rates, and so on since June 2021, and hence levels estimates may be under- or over-estimating the true values and should be used with caution. Estimates of rates will, however, be robust.</p>

【背景】
劳动力调查（Labour Force Survey, LFS）是一套基于国际就业、失业及经济非活动定义的独特信息来源，涵盖职业、培训、工作时长以及16岁及以上家庭成员的个人特征等众多相关议题，可用于为社会、经济与就业政策制定提供参考。该调查最早于1973年至1983年间以两年一期的频率开展。1984年至1991年间，调查改为年度开展，包含全年进行的季度调查以及春季季度的“补充”调查（此后数据按季度采集）。1992年起，季度数据正式对外发布，季度样本量大致等同于此前的年度样本量，该调查也自此更名为季度劳动力调查（Quarterly Labour Force Survey, QLFS）。1994年12月起，北爱尔兰的数据采集转为完整的季度周期，与英国其他地区保持一致，自此QLFS覆盖全英国（不过英国数据档案馆仍留存有部分额外的北爱尔兰年度LFS数据集）。如需了解QLFS的更多背景信息，可查阅相关文档。

【纵向数据】
LFS会将每个样本家庭保留连续五个季度，每季度替换五分之一的样本。该调查最初设计用于生成截面数据，但目前已将每个个体的相关数据进行关联，以提供纵向信息。纵向数据包含两类通过加权方法调整无应答偏差的关联数据集：两季度数据集关联连续两波调查的数据，五季度数据集则关联一整年（例如2010年1月至2011年3月，含首尾月份）的全部五波调查数据，并涵盖所有相关个体信息。完整的纵向数据序列可追溯至1992年冬季。通过关联记录构建纵向维度，可提供不同劳动力类别（就业、失业及经济非活动群体）间随时间变化的总流动信息，进而明确在各类别间流动的人群特征。此外，纵向信息有助于监测政府政策的实施效果，可用于追踪受特定政策举措影响人群的后续活动与处境，并与其他人口群体进行对比。不过，这种纵向关联过程可能会带来方法学层面的问题，进而扭曲数据结果。英国国家统计局（ONS）仍在持续研究此类问题，并建议对结果的呈现需谨慎考量，必要时需在输出结果中附带相关警示说明。

【LFS文档】
英国数据档案馆可获取的LFS数据集配套文档，主要包含各年度对应问卷的最新版用户指南手册。不过，ONS会定期更新相关手册，因此建议用户在开展分析前，先前往ONS的<a href="https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/methodologies/labourforcesurveyuserguidance" title="劳动力调查用户指引" target="_blank">劳动力调查用户指引</a>页面查阅最新文档。这一点对于使用早期QLFS数据集的用户尤为重要，因为用户指南中的相关信息与指引可能已随时间发生变化。

【2021年与2022年数据文件的职业数据】
ONS已发现其多项调查在2021年与2022年的数据文件中存在部分职业数据采集问题。尽管ONS估算整体影响较小，但该问题会影响部分细分（四位数字）标准职业分类（Standard Occupational Classification, SOC）职业的分类数据精度，以及基于此类数据衍生的相关结果。更多详细信息可参阅ONS于2023年7月11日发布的文章：<a title="英国ONS劳动力调查中错误编码职业数据的修订：2021年1月至2022年9月" href="https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/articles/revisionofmiscodedoccupationaldataintheonslabourforcesurveyuk/january2021toseptember2022">《英国ONS劳动力调查中错误编码职业数据的修订：2021年1月至2022年9月》</a>。

【2022年加权方案】
最新LFS估算所使用的人口总量，基于2021年的人口模式，采用了英国、欧盟及非欧盟人口的实时信息（Real Time Information, RTI）数据的预测增长率。因此，本次LFS所使用的总人口未考虑2021年6月以来移民、出生率、死亡率等因素的变化，由此得到的人口水平估算值可能与真实值存在偏差，使用时需谨慎。不过，相关比率估算结果仍具备稳健性。