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Flow data

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Origin-destination data (also known as flow data) will include the travel-to-work and migration patterns of individuals, cross-tabulated by variables of interest (for example occupation). New products for the 2011 Census will also provide the migration patterns of those living at a student  address one year ago and provide information on individuals with second residences.

A large amount of the origin-destination data will be at UK level, providing flows for usual residents of England, Wales, Scotland, and Northern Ireland. Any statistics that cannot easily be harmonised across the UK due to differences in the data collected will be provided for usual residents of England and Wales only. These statistics will still provide geographical detail of any flows between the other countries of the UK.

The travel-to-work data for England and Wales will use the new workplace zone geography to show flows between output areas of usual residence to workplace zones.

Disclosure control

All population estimates, including small estimates, will be permitted in principle. However, ONS has an obligation to protect the attributes of identified individuals and may revise table designs if they are deemed disclosive on completion.

The UK Statistical Disclosure Control policy states that the protection of the most detailed origin-destination tables will come from the licensing/access conditions. This is a change from the 2001 Census, where the protection for similar outputs came from the post-tabular small cell adjustment which still allowed wide and easy access, but also adversely affected the utility of the outputs.

For more information on the statistical disclosure control policy for origin-destination tables, please read section 8 of the Statistical disclosure control for 2011 Census.

Access conditions

There will be a small number of tables that are available publicly, however, the majority will only be available as secure files under certain access conditions.

The more detailed tables and those at lower levels of geography will only be available as secure data within a secure environment. The secure data will be held in ONS's Virtual Microdata Laboratory (VML) in the long term, however ONS are currently working on a project to update the VML and options for how the secure origin-destination data can be made available before the new VML is launched, likely to be towards the end of 2014, are being investigated.

The VML is currently only available for research purposes conducted by an Approved Researcher. Read about how to be accepted as an Approved Researcher.

ONS cannot yet accept requests for access to origin-destination data. We will provide more information on how to do this closer to the time of release.

Some of the less detailed tables will be treated as safeguarded files and will either be made available to researchers to hold outside of ONS under strict terms and conditions or will be available within a secure ONS environment. Different access arrangements are being put in place for different types of users to maintain public confidence in ONS's protection of confidentiality of the data.

Access to these tables outside of ONS will be available through the UK Data Service, but will be limited to users from academia and the public sector. Any other users who wish to access the safeguarded data will have to do so using an alternative method. ONS are exploring the possibility of placing the data in the VML, but allowing commercial organisations and other users such as charities and the general public access to the data without the full terms and conditions for access to, and use of, the VML being applied, i.e. it would not be necessary to be registered as an Approved Researcher. Any outputs or analysis produced would be subject to disclosure checks before approval could be given for users to take them outside of the VML.

The table below summarises how it is proposed to make the safeguarded and secure data available to different types of users, however please be aware that making safeguarded data available in the VML is only being investigated as an option at this stage. More information about the different terms and conditions and how to obtain access to the tables will be made available shortly when arrangements have been finalised.

Safeguarded data Secure data
Academics UK Data Service VML (Approved Researcher status required)
Government and public sector UK Data Service VML (Approved Researcher status required)
Commercial organisations VML (Approved Researcher status not required) VML (Approved Researcher status required)
Other VML (Approved Researcher status not required) VML (Approved Researcher status required)

Table specifications for all origin-destination tables are available; see Flow data table layouts. These specifications provide confirmation of the geographies that will apply to each table, as well as a provisional indication of whether each table will be public, safeguarded or secure. However, this is only a provisional indication and each dataset will have to be assessed for disclosure before a final decision on the access channel is made. It is possible that some of the tables indicated as being secure may be able to be made available via the safeguarded channel.

Publication

The first batch of origin-destination tables was released on 25th July 2014. There were two releases:

1. Origin-destination statistics on migration, workplace and students for local authorities in the United Kingdom, and

2. Origin-destination statistics on second residences and workplace for merged local authorities and middle layer super output areas (MSOAs) in England and Wales.

The UK release consists of 11 tables (52 Kb Excel sheet) , all at local authority level. The scope of this release changed from that previously announced, with only the three workplace tables covering the whole of the UK. The other four, previously announced, tables covering migration and students are available for England and Wales and Northern Ireland only, and do not cover the whole of the UK. National Records for Scotland, which is responsible for the 2011 Census in Scotland, has identified an issue with the Scottish results that needs resolving before the data can be published. The statistics for England and Wales are provided in separate tables to the statistics for Northern Ireland, giving a total of eight tables rather than the four tables announced previously. Tables covering the whole of the UK will be published later in the year when this issue has been resolved, and a release date will be published on this page when it can be confirmed.   

The England and Wales release consists of nine tables (47.5 Kb Excel sheet) , six at local authority level and three at middle layer super output area (MSOA) level. This release is not affected by the issue with the Scottish results, and was published as originally planned.

An additional 12 tables for the UK, produced at one or more levels of geography, have been identified as priority tables, and work is currently underway to make these tables available to users as soon as possible. Four of these tables are affected by the issue with the Scottish results, meaning that the tables will be provided for England, Wales and Northern Ireland only in the short-term, with full UK results published later in the year when the issue has been resolved. Again, the statistics for England and Wales will be provided in separate tables to the statistics for Northern Ireland. In addition, multiple geographies are published in separate tables, giving a total of 24 tables. These tables will not be available publicly due to the level of disclosure in the tables, and instead  will made be available as either safeguarded or secure files, under access conditions.

Safeguarded tables: The safeguarded tables (35.5 Kb Excel sheet)  are likely to be released in September 2014. This is a delay from the original planned date of August 2014 as ONS want all users to be able to access the data at the same time and therefore need to ensure all types of users can access the data before it is released. As these tables will not be available in the public domain with equal access for all, the release of these tables will not be announced in the ONS Release Calendar. However, the release date for these tables will be published on this page when it is confirmed, along with information on how to apply for access to the tables. Please note that Statistical Disclosure Control checks are still being carried out on these tables, and it cannot yet be confirmed that these tables will all be released as safeguarded data. 

Secure tables: Work is ongoing on an interim solution to make the secure tables (44 Kb Excel sheet) available before the new VML is launched later in 2014, and it is hoped that this solution will be in place in September 2014. The migration tables will be released for England, Wales and Northern Ireland only in the short-term, with full UK results published later in the year when the issue has been resolved. As with the safeguarded tables, the release of the secure tables will not be announced in the ONS Release Calendar, but the release date will be published on this page when it is confirmed, along with information on how to apply for access to the tables. ONS will not accept any requests for access to this data before this time. It is expected that the approval process to gain access to the secure data in the Virtual Microdata Laboratory will take approximately 2-3weeks.   

The current proposed timetable for the release of the remaining origin-destination products is for the secure files to be made available in November 2014, and the safeguarded files to be made available in December 2014. However, these dates are not yet confirmed and are subject to change. It is expected that all of the tables that can be made available publicly will have been included in the July release, (apart from those affected by the Scotland issue which we will release as soon as possible). However, until Statistical Disclosure Control checks have been carried out on each of the tables the release channel cannot be confirmed.

The issue found with the Scottish results also affects the European Commission Census Regulation Statistics which were released in March 2014, and the planned release of migration statistics for the UK.

 

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