Data Linking
Data linking refers to a process whereby records from one survey (in this case, WERS) are linked with records for the same unit from a different survey, or with information held about that unit in an administrative database.
As this type of 'external data linking' requires access to identifiable information about the surveyed units, it can only take place under special conditions (described below). These special conditions do not apply to the 'internal' linking of the different datasets within WERS (e.g. linking the workplace data from the MQ with the employee data from the SEQ: this can be done with the general use data file).
'External data linking' is possible for the 2,477 workplaces in WERS 2011 where managers consented to the linking of WERS data with other data sources (MQ Question MLINKDAT=Yes). This is subject to the requirement that the resulting linked data remains anonymised and is only used for statistical and analytical purposes.
It should be noted that external data linking is only possible at the level of the business unit (MQ). None of the individual employee respondents are identifiable in WERS; accordingly it is not possible to link data on individual employees, employee representatives or managers in WERS with employee-level data from other sources.
How is it done?
Academic users in the UK can undertake such data linking by utilising the 'Secure access' version of the WERS data deposit. This version of the WERS data can be accessed through the Secure Access web portal provided by the UK Data Service. UK government researchers can link the data within the ONS' Secure Data Service.
The WERS dataset deposited with Secure Access and ONS contains the Inter-Departmental Business Register (IDBR) Local Unit reference number attached to each workplace when it was sampled from the IDBR (September 2010 in the case of the refreshment sample; September 2003 in the case of the panel). The dataset also contains the IDBR reference numbers for the Reporting Unit and Enterprise to which the Local Unit belonged at the point of sampling. These IDBR reference numbers allow the WERS records to be linked to records in the ONS Business Structure Database (BSD), the Annual Respondents Database (ARD), the Annual Survey of Hours and Earnings (ASHE) and any other surveys/databases which contain IDBR reference numbers.
Through the link to the IDBR, it has also been possible to link WERS records to Companies House Reference Numbers (CRNs), which would in principle facilitate a link to the FAME database of company accounts.
The WERS data deposited with Secure Access and ONS also contains the postcode for each surveyed establishment, enabling analysts to attach area-level data (e.g. local unemployment rates) to the WERS records.
Do I need special permissions to link the data?
The UK Data Service and ONS each have standard registration processes for users who wish to use the 'Secure Access' version of the WERS data. There are three steps in the process:
1. Apply to become an Accredited Researcher
2. Apply to set up a new 'Secure Access' project using WERS (or add WERS to an existing project)
3. Attend a half-day training course
Once you have the status of 'Accredited researcher' and have set up a project to use WERS, you will be able to link the WERS data to other datasets that are held within the secure environment, and you will be able to conduct analyses using these linked data. You will not be able to remove the linked data from the secure environment; you may only export your research results. The UKDS and ONS facilities have standard procedures for checking your output, so as to ensure that any material that you wish to remove from the secure environment does not disclose the identity of the survey participants.
Users who wish to access the Secure Access version of the WERS data through the UK Data Service should note that the 'General Use' file and 'Secure Access' files have separate entries in the UKDS data catalogue:
Entry for the Secure Access version of the WERS data in the UK Data Service catalogue
Practicalities of linking to specific datasets
An important issue when seeking to link WERS to other datasets is the correspondence between survey units. The 2011 WERS is a survey of workplaces - or 'local units' in the language of official statistics. Many other business surveys take the firm (or 'enterprise') as the unit of observation. Others allow the firm itself to decide its own 'reporting units'. The distinction between local units, reporting units and enterprises is explained on the ONS' IDBR webpage.
Some of the issues that arise with specific datasets are described below:
Linking with the ONS Annual Respondents Database (ARD) or Annual Business Survey (ABS):
The ARD/ABS does not offer Local Unit data; WERS Local Units can only be matched to ARD Reporting Units (which typically cover whole enterprises). A broader discussion of the practicalities of linking WERS (2004) and the ARD can be found in WERS 2004 Technical Paper No. 1.
A comparison of the subjective and objective performance data in WERS (2004) is provided in WERS 2004 Technical Paper No. 2.
Linking with the ONS Annual Survey of Hours and Earnings (ASHE):
The ASHE dataset does not contain an IDBR Local Unit identifier. However the employee records in ASHE do contain the IDBR Enterprise reference number for the employing organisation and also the postcode for the employing workplace. The combination of IDBR Enterprise reference number and postcode enables a link to be established between ASHE employees and WERS workplaces. A discussion can be found in WERS 2004 Technical Paper No. 3.
Linking with area-level data:
Matching area-level data onto WERS via the workplace postcode will typically be facilitated by using the ONS Postcode Directory (ONSPD), which links postcodes to broader geographical units such as Travel to Work Areas. The ONSPD is available to download, free of charge, from the ONS Open Geography Portal.
