Labour Force Survey Two-Quarter Longitudinal Dataset, January - June, 2021

<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>
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<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><span style="font-weight: bold;">New reweighting policy</span><br>Following the <a href="http://doc.ukdataservice.ac.uk/doc/8343/mrdoc/pdf/biennial_lfs_aps_reweighting_policy.pdf" target="_blank" style="background-color: rgb(255, 255, 255);">new reweighting policy</a> ONS has reviewed the latest population estimates made available during 2019 and have decided not to carry out a 2019 LFS and APS reweighting exercise. Therefore, the next reweighting exercise will take place in 2020. These will incorporate the 2019 Sub-National Population Projection data (published in May 2020) and 2019 Mid-Year Estimates (published in June 2020). It is expected that reweighted Labour Market aggregates and microdata will be published towards the end of 2020/early 2021.<br>
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<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">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>
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<b> Additional data derived from the QLFS</b><br>
The Archive also holds further QLFS series: End User Licence (EUL) quarterly data; Secure Access datasets; household datasets; quarterly, annual and ad hoc module datasets compiled for Eurostat; and some additional annual Northern Ireland datasets. <br>
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<b>Variables DISEA and LNGLST</b><br>
Dataset A08 (Labour market status of disabled people) which ONS suspended due to an apparent discontinuity between April to June 2017 and July to September 2017 is now available. As a result of this apparent discontinuity and the inconclusive investigations at this stage, comparisons should be made with caution between April to June 2017 and subsequent time periods. However users should note that the estimates are not seasonally adjusted, so some of the change between quarters could be due to seasonality. Further recommendations on historical comparisons of the estimates will be given in November 2018 when ONS are due to publish estimates for July to September 2018. <br>
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An article explaining the quality assurance investigations that have been conducted so far is available on the <a href="https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/methodologies/analysisofthediscontinuityinthelabourforcesurveydisabilitydataapriltojune2017tojulytoseptember2017" target="_blank">ONS Methodology</a> webpage. For any queries about Dataset A08 please email [e-mail].<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> <p><span style="font-weight: bold;">Latest edition information</span></p><p>For the fourth edition (February 2025), the data file was resupplied with the 2024 weighting variable included (LGWT24).</p>

**背景**
《劳动力调查（Labour Force Survey, LFS）》是采用国际通用的就业、失业及经济不活跃群体定义，同时涵盖职业、培训、工作时长以及16岁及以上家庭成员个人特征等多类相关主题的独特信息来源，可为社会、经济与就业政策制定提供决策参考。该调查最初于1973年至1983年间每两年开展一次；1984年至1991年改为年度调查，由全年开展的季度调查与春季季度的“补充”调查组成（此后数据按季度收集）。1992年起，调查开始提供季度数据，季度样本量大致与此前年度调查的样本量相当，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覆盖英国全境（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背景的更多信息，可查阅相关官方文档。

**纵向数据**
LFS会将每个样本家庭保留连续五个季度，每季度更换五分之一的样本。最初的调查设计仅用于生成横截面数据，但目前已将每个受访者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回应偏差的关联数据集：两季度数据集关联连续两轮调查的数据，五季度数据集则覆盖完整一年（例如2010年1月至2011年3月，含首尾时段），包含全部五轮调查的数据。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，例如可以呈现不同劳动力市场类别（就业、失业及经济不活跃群体）间随时间变化的总流量信息，详细展示跨类别的流动人群情况。此外，纵向信息可用于监测政府政策的实施效果，追踪特定政策举措影响人群的后续活动与境况，并与其他人口群体进行对比。不过，此类纵向数据关联可能存在方法学问题，进而扭曲数据结果。英国国家统计局（Office for National Statistics, ONS）仍在持续研究此类问题，并建议对结果的呈现方式需谨慎考量，必要时需在输出结果中附上相关警示说明。

**新加权政策**
根据<a href="http://doc.ukdataservice.ac.uk/doc/8343/mrdoc/pdf/biennial_lfs_aps_reweighting_policy.pdf" target="_blank">新加权政策</a>要求，ONS已审查2019年期间公布的最新人口估算数据，并决定不再开展2019年LFS与住户调查（Annual Population Survey, APS）的加权工作。因此，下一次加权工作将于2020年进行，届时将纳入2019年地方人口预测数据（2020年5月发布）与2019年年中人口估算数据（2020年6月发布）。预计经加权处理的劳动力市场汇总数据与微观数据将于2020年末/2021年初发布。

**LFS文档说明**
档案馆提供的LFS数据集配套文档，主要包含各年度对应用户指南手册的最新版本与相应年度的调查问卷。不过，ONS会定期更新用户指南手册，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="劳动力调查用户指南">劳动力调查用户指南</a>页面查看最新文档。**对于早期QLFS数据集的用户而言，这一点尤为重要，因为用户指南中的信息与指引可能已随时间发生变化。**

**QLFS衍生附加数据**
档案馆还留存有其他QLFS系列数据：最终用户许可（End User Licence, EUL）季度数据、安全访问数据集、家庭数据集、为欧盟统计局（Eurostat）编制的季度、年度及专项模块数据集，以及部分额外的北爱尔兰年度数据集。

**DISEA与LNGLST变量说明**
ONS曾因2017年4月至6月与2017年7月至9月的数据存在明显间断，暂停了数据集A08（残疾人群体劳动力市场状况）的发布，现已恢复该数据集的提供。鉴于此次数据间断及现阶段调查结果尚不明确，在对2017年4月至6月与后续时段的数据进行对比时需格外谨慎。同时需注意，该估算数据未经过季节性调整，因此季度间的部分变化可能源于季节性因素。ONS将于2018年11月发布2018年7月至9月的估算数据时，针对历史数据对比的相关建议作出进一步说明。

一篇阐述当前已完成质量保证调查的文章可在ONS的<a href="https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/methodologies/analysisofthediscontinuityinthelabourforcesurveydisabilitydataapriltojune2017tojulytoseptember2017" target="_blank">方法学</a>页面查阅。若对数据集A08有任何疑问，请发送邮件至[e-mail]。

**2021年与2022年数据文件的职业数据说明**
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））职业的分类数据准确性，以及基于此类数据衍生的统计结果。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劳动力调查中编码错误职业数据的修订：2021年1月至2022年9月》" href="https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/employmentandemployeetypes/articles/revisionofmiscodedoccupationaldataintheonslabourforcesurveyuk/january2021toseptember2022">《英国ONS劳动力调查中编码错误职业数据的修订：2021年1月至2022年9月》</a>。

**2022年加权处理**
最新LFS估算所使用的人口总量，基于2021年的人口模式，采用英国、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，LFS所使用的总人口数未考虑2021年6月以来移民、出生率、死亡率等因素的变化，故而总量估算值可能高估或低估真实数值，使用时需谨慎。不过，比率估算值仍具备稳健性。

**最新版本信息**
第4版（2025年2月）的数据文件已重新提供，并纳入了2024年的加权变量（LGWT24）。