DWP have provided the following updated guidance notes.
Statistics on vacancies notified to and handled by Jobcentre Plus are derived as a by-product of administrative systems and published monthly on the Nomis website. Users should be aware of the following points when using and interpreting the series:
Economy coverage. They are not whole-economy figures. Coverage relates just to vacancies notified to Jobcentre Plus and as such represent a market share of vacancies throughout the whole economy. This proportion varies over time, according to the occupation of the vacancy and industry of the employer, and by local area. Estimates of the stock of unfilled vacancies across the whole economy are published by the Office for National Statistics (link below) albeit not across the range of breakdowns available for Jobcentre vacancy statistics.
ONS Vacancy Survey (link)
Geographic coverage. Coverage is for Great Britain. Jobcentre vacancy data for Northern Ireland are available separately from Northern Ireland Labour Market Reports.
Time series. The time-series is susceptible to discontinuities arising from changes to vacancy taking (e.g. 2001 introduction of Employer Direct/online), and vacancy handling (e.g. 2006 changes to employer follow-up processes). A fuller technical report, originally published in the June 2005 issue of Labour Market Trends, is available from the link below:
Publication of Jobcentre Plus vacancy statistics (pdf, 104kb)
Flows data. Flows data labeled as 'month X' predominantly relate to the previous month. The Release Calendar gives the monthly release dates and the associated count dates (https://www.nomisweb.co.uk/home/release_dates.asp). Flows figures relate to the period from the count date in the month requested to the count date in the previous month. To illustrate, Jan-09 flows data cover the period 6 Dec to 2 Jan, Feb-09 flows the period 3 Jan to 6 Feb, Mar-09 flows the period 7 Feb to 6 Mar.
The monthly flow data are not standardised. Reporting months relate to either a 4 week or 5 week period depending on count dates. Users should be cautious about comparing monthly flows and may wish to standardise the figures to 4.33 week month. To illustrate, the Jan-09 period is a 4-week period, Feb-09 is a 5-week period, and Mar-09 a 4-week period.
Local area geographies. Data for a range of local area geographies is available. In the main (95% of cases) the postcode of the vacancy is used to allocate the vacancy to a local area - be it output area, local authority district, or parliamentary constituency. Where this is missing or invalid, the employers' postcode is used (4% of cases). In the absence of both a valid vacancy and employer postcode, the postcode of the Jobcentre Plus office designated as owning the vacancy is used to ensure that all vacancies are allocated a valid postcode.
MoD vacancies. Local area data can throw up spurious figures. For example, Lincoln local authority includes all national vacancies notified by the Ministry of Defence since these are recorded against a single central postcode irrespective of actual location.
Jobs Warehouse vacancies. For employers and agencies that do not require the additional services offered by Jobcentre Plus of matching clients to employers vacancies, a Jobs Warehouse has been developed allowing recruiters to provide information direct to a central database. Vacancies notified by this route are not included in the statistical series.
Unfilled vacancies. Users of the unfilled vacancies series should generally use the live unfilled variable since this will reflect vacancies actively available to jobseekers at a point in time. The count of total unfilled vacancies also includes those which have been suspended pending closure and as such are not available to users at that point in time.