1. Introduction

During the coronavirus (COVID-19) pandemic, we have been providing timely indicators of the effect of the disease on the UK economy and society in our Coronavirus and the latest indicators for the UK economy and society bulletin.

These faster indicators now include a set of experimental job advert indices covering the UK job market. These indices are created based upon job adverts provided by Adzuna. These data include information on over 36 million job advert entries live during the period February 2018 to May 2020 broken down by job category based on the job details. This note sets out the methodology used to derive these indices and provides comparisons with other data sources.

As Experimental Statistics, these data are subject to revisions as our methodology and systems are refined.

We plan to develop these indicators iteratively over the coming weeks and months, taking on user feedback, and to produce further breakdowns including online vacancies by Standard Occupational Code and by region.

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2. What data source are we using?

Adzuna is an online job search engine that collates information from thousands of different sources in the UK. These range from direct employers’ websites to recruitment software providers to traditional job boards thus providing a comprehensive view of current online job adverts.

Adzuna is working in partnership with the Office for National Statistics (ONS) and has made data available for analysis including online advert job descriptions, job titles, job locations, job categories and salary information. The data provided are a point-in-time estimate of all job adverts indexed in Adzuna’s job search engine during the point of data extraction.

Prior to our analysis, Adzuna carries out some data cleaning methods such as removing duplicate entries where all information relating to a job advert is the same, because of multiple recruiters advertising at the same time, as well as applying minimum quality thresholds on some data fields. Adzuna also uses a neural network to assign categories to the job adverts. This model uses natural language processing to analyse the text in both the job title and description fields, and uses these data to assign the most suitable job category.

Adzuna has a high coverage of all job adverts in the UK but because of the fact that this source is limited to online vacancies, there will be some job adverts missed such as casual work advertised through word-of-mouth and internal vacancies, which are filled using other head-hunting methods.

If you would like more information about Adzuna's data, please contact james@adzuna.com

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3. How we measure online vacancy data

We are using online job advert data to create a proxy measure of overall vacancies in the UK. This measure is presented as an index, which is calculated in the following way:

  1. Aggregate all live job adverts at a given point in time in a week
  2. Missing and anomalous values are imputed by linear interpolation, so there is one value for each week.
  3. The mean of weekly counts of live job adverts listed on Adzuna in 2019 is calculated, including the imputed values.
  4. Each value in the total time series is divided by this mean value, thus indexing the series so the 2019 average equals 100.
  5. The indexed values are then rounded to one decimal place.

Notes for: How we measure online vacancy data

  1. The education industry's total adverts for the 21 March was anomalous and the value has been imputed through linear interpolation.

  2. The missing values are one week between 15 and 28 February 2019, three weeks between 31 October and 28 November 2019, two weeks between 5 and 27 December 2019 and one week between 3 and 16 January 2020.

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4. Strengths and limitations

Strengths of Adzuna data

  • The data are extremely timely with analysis available to be published six days after the snapshot of adverts has been extracted; this provides an early indication of how the trend of the number of live job adverts is changing in the UK.
  • Data are available on a weekly basis, allowing week to week comparisons.
  • The data are very granular, with investigations into meaningful analysis by lower-level geographies and detailed sectors of the economy.

Limitations of Adzuna data

  • The number of job adverts being posted is not a direct measure of labour force demand; the number could respond to other changes such as how positions are recruited for, that is, decreased activity from recruitment agencies could lead to decreased duplication of multiple adverts for one post.
  • Job adverts may not be removed from online job vacancy boards immediately when the position is filled so the indices may not fully reflect companies who have halted active recruitment. Note that Adzuna perform data cleaning to remove adverts that have not been observed as live for 30 days.
  • The data are compiled from multiple job vacancy boards and adverts are considered “live” if the posting is still live on any board, even when it has already been removed from an alternative source.
  • The scope of online job adverts does not fully capture the scope of UK economic activity because of differing advertising methods, for example, casual work may be advertised by word-of-mouth or in shop windows as opposed to online.
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5. Existing measures of vacancies – ONS Vacancy Survey

The Vacancy Survey is a statutory, monthly survey of businesses. The survey asks a single question: how many job vacancies a business had in total (on a specified date) for which they were actively seeking recruits from outside their organisation.

The headline series are based on three-month moving averages, by industry and by size of business. The Inter-Departmental Business Register (IDBR) is used as the sampling frame. The total sample is approximately 6,100 businesses per month, with approximately 1,400 large businesses included every month and the remaining 4,700 consisting of smaller enterprises randomly sampled on a quarterly basis.

The survey covers all sectors of the economy and all industries in England, Scotland and Wales (Great Britain) with the exception of employment agencies (to avoid double-counting of vacancies) and private households, agriculture, forestry and fishing (because of the disproportionate costs involved as these industries mainly consist of very small businesses with few vacancies). Estimates for UK are derived by weighting up the data for Great Britain using employment estimates (Northern Ireland accounts for around 3% of UK employment). Vacancy statistics are not available by region. Northern Ireland businesses are not approached because of the risk of overlap with other surveys conducted by Northern Ireland departments.

The Vacancy Survey reference date falls on the first Friday of the month, unless this is the first day of the month. In this case, the reference date moves to the second Friday of the month. For the May 2020 period, the reference date was Thursday 7 May 2020 because of a change in date of the first May Bank Holiday.

ONS vacancy statistics are a three-month average measure, which are seasonally adjusted and then published in the Vacancies and jobs in the UK statistical bulletin, usually between six and seven weeks after the reference date of the survey.

Further information regarding the ONS Vacancy Survey can be found in the online Quality and Methodology Information.

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6. Comparison with the ONS Vacancy Survey

When comparing experimental Adzuna job adverts data with the Office for National Statistics (ONS) Vacancy Survey it is important to be cautious and note the different definition of what each source covers.

  • Adzuna covers online job adverts listed, which can include multiple job opportunities within one advert or ongoing recruitment campaigns, which do not align directly with one job vacancy; further detail on the limitations of the Adzuna dataset can be found in Section 3.
  • The ONS Vacancy Survey covers vacancies defined as a vacancy for which businesses are actively seeking recruits from outside their organisation.

However, it may still be sensible to compare both data sources to give an indication of quality. At a higher level we can see similar movements in Adzuna vacancies compared with ONS vacancies data. The same comparability can be observed with vacancies that are classified at industry level with equivalent Standard Industrial Classification (SIC), such as “Education”, “Healthcare/Social Care” (aggregated from Healthcare and Social Care), “Retail/Wholesale” and “Catering/Hospitality”. For these groups, we found some correlation with trends in ONS vacancies data.

However, this correlation was not found in other groups because of different methodologies. The vacancies data in some categories assigned by Adzuna such as “Graduates” and “IT/Computing/Software” are linked to both occupations and industries, therefore it is not appropriate to compare industry-level vacancies directly with the ONS vacancies estimates which are produced at SIC level.

While the "Health/Social care" category has historically shown a strong correlation with the ONS Vacancy Survey, from April 2020, it has increasingly diverged from the vacancies data.

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7. Comparison with Institute for Employment Studies

The Institute for Employment Studies (IES) is currently publishing weekly vacancy analysis using Adzuna data. These publications provide additional insight including local changes in vacancy levels and changes in vacancies by salary levels. We are working in collaboration with IES to ensure our methodologies are consistent but there are some differences which users should be aware of.

Extract date

Adzuna provide point-in-time estimates of job adverts listed at any given time. Although both the Office for National Statistics (ONS) and IES are extracting their data weekly, these extractions take place on different days of the week. This means there are minor differences in our analyses, as there are a different number of job adverts listed on different days.

Location assignment

Some of the job adverts included in the Adzuna data have unidentified locations. IES has removed these adverts from their total advert series, but the ONS has not. This may cause minor differences between the sources at the aggregate level.

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Contact details for this Methodology

Laura Caldwell
vacancy.survey@ons.gov.uk
Telephone: +44 (0) 1633 455955