Transforming population and migration statistics: Patterns of circular movement into the UK

Transforming population and migration statistics
Case Study: Patterns of circular movement into the UK
Centre for International Migration
Published: 30th January 2019
Coverage: Exit Checks data covering April 2015 – April 2018
Disclaimer: These Research Outputs refer to patterns of circular
movement of visa nationals into and out of the UK from Home
Office Exit Checks data and are not Official Statistics. These
outputs must not be interpreted as an indicator of circular
migration.
Key messages
Home Office Exit Checks data is a key source for analysing circular patterns of movement. By this we mean patterns of
movement where individuals cross the UK border multiple times in a given time period.
We can use these data to start to understand different patterns of movement and reasons for that movement.
Initial analysis of Exit Checks data provided to ONS by Home Office reveals substantial variation within the group of people we
can observe with circular patterns of movement.
From our analysis we have identified broad groups of people of interest, and also key areas where we need to develop our
understanding further, in collaboration with Home Office colleagues.
International students are an area of particular interest for ONS, due to the challenges of measuring them with the International
Passenger Survey. This work has helped us to identify future work we can undertake to better understand how this group appear
in our estimates and where their movement patterns are circular.
What can using Exit Checks data tell us about circular patterns of movement into and out of the UK?

Why is this research important?
Circular migration is an area stakeholders have asked us to examine, and which ONS does not explicitly
cover. We know that our existing estimates and definitions will capture some people with circular patterns of
movement and as ONS examines the use of administrative data, it becomes increasingly important to
understand population groups whose patterns of movement may challenge our existing definitions, as well as
those that may not get captured in existing sources.
Background
This case study aims to examine the use of Exit Checks data to better
understand how circular movement patterns can be measured and
defined in the UK context
Data sources Home Office Exit Checks data
Time period Moves occurring between April 2015 and April 2018.
Population coverage Non-EEA nationals with multiple stays in or out of the UK, who registered at least
one arrival between 8th April 2015 and 8th April 2016, who held or went on to
hold a non-visit visa. Analysis covers those who went on to make multiple moves
within the next 2 years from their qualifying arrival. EEA nationals are not
covered by Exit Checks data held by ONS.
Methodology See slide 5
Things you need to know See slide 13

Background
There are various definitions, but a 2016 UNECE report1 defines it as:
Conceptual definition
“[A] repetition of legal migration by the same person between two or more countries.”
Statistical definition (long-term)
“A circular migrant is a person who has crossed the national borders of the reporting country at
least 3 times over the past 10 years, each time with duration of stay (abroad or in the country)
of at least 12 months.”
These definitions give a good basis for looking at long term circular migration, but we
are also interested in shorter term patterns of circular movement which may indicate
circular migration.
Aims of this project :
To understand the movement patterns of people who can be seen to have multiple moves within
Exit Checks.
Understand how frequent movers should be interpreted with regard to inclusion in migration and
population estimates, and work to understand how UK society and economy is impacted by
these people.
Work to understand the movement patterns of people with circular or very frequent movement
patterns. This work will help us understand how to measure and talk about these people.
1 https://www.unece.org/fileadmin/DAM/stats/documents/ece/ces/bur/2016/February/14-Add1_Circular_migration.pdf

We have described the patterns we have seen as circular patterns of movement, rather than
circular migrants. This is because at this stage we don’t know enough about them and their
intentions and activities to meet existing definitions of “migration”.
To get to an understanding of circular migration, we first need to understand circular patterns of
movement, and that’s the focus of this phase of analysis.
We have initially identified 4 groups we are interested in looking at in more detail, as shown
here.
The data ONS obtained only covers those who held at least one non-visit visa, at some
point in the period 8th April 2015 to 8th April 2018. Therefore those who only exclusively
held visit visas in this time period are excluded from this phase of work.
Low frequency circular movement group
• People who have 2 to 5 journeys.
• People who have stays, both inside and outside the
UK, lasting at least 30 days each.
Medium frequency circular movement group
• People who have stays, both inside and outside the
UK, lasting at least 30 days each.
High frequency circular movement group
• People who have spent at least six months, in total,
outside the UK during the two-year period.
Very high frequency circular movement group
• People who have 30 or more journeys.
• People who have spent at least six months, in total,
outside the UK during the two-year period.
Classification of circular patterns of movement

Volumes of circular patterns of movement, found in Exit Checks for our time
period.
Group Number in
group
Low frequency 304,000
Medium frequency 148,000
High frequency 15,000
Very high frequency 12,000
• Our first examination of the data showed there was a
huge amount of variation in peoples travel patterns. To
make analysis easier, we created 4 groups to look at.
• The groups were created based on patterns of movement
and length of stay inside/outside the UK. In our future
work plans we will be doing more work to understand
how changing the borders between these groups affects
our numbers and conclusions.
• This table gives the indicative volumes we have identified
from our groups. These are not intended to be definitive,
or show the total volume of potential movers.
• The people of interest were selected as those with records within Exit Checks for whom their first arrival
in the UK was between 8th April 2015 – 8th April 2016.
• We then followed each identified person for two years from their first arrival date to identify how many
journeys (each journey includes an in and out movement) they recorded.
• For those with a low or medium frequency of journeys, only stays of over a month inside or outside the
UK were counted, to eliminate typical holidaymakers.
• For high and very high frequency of journeys, we looked at their total length of stay outside the UK
instead (a total of six months or more outside the UK over the two-year period, rather than length of
individual stays).
Source: ONS analysis of Home Office Exit Checks data

The characteristics of the different groups can be seen from our analysis, with
clear groups emerging.
Group Number in
group
Patterns of movement within group Modal demographics of group
Low frequency 304,000 • Avg length of stay in UK per visit – 4
months.
• Avg length of stay outside UK per
visit – 5.5 months.
• Visa – Student T4
• Nationality – Chinese
• Age grp – 20-30
Medium frequency 148,000 • Avg length of stay in UK per visit –
2.5 months.
• Avg length of stay outside UK per
visit – 3 months.
• Visa – Student T4
• Nationality – Chinese
• Age grp – 20-30
• Our initial rules for identifying people with circular movement patterns showed that our low
frequency mover group was the biggest group, followed by our medium frequency mover
group.
• Initial work on these groups suggests there may be overlap between them which could be
investigated by looking at the impact of changing the boundaries and rules for each group.
• Student visas make up the most numerous single component of the low and medium
frequency groups.
• The most common nationality of this group was Chinese, but this is strongly related to the
study visas.
• If study visas are removed, then Indian nationals and standard visit visas are the most
common groups.

The characteristics of the different groups can be seen from our analysis, with
clear groups emerging.
• Our results here must be seen in the context of who is included in our data extract i.e. those here on a non-
visit visa between 8th April 2015 and 8th April 2016. This means that we do not have information on those
coming to the UK for visits only – but that we do have information on people who came for e.g. work or
study, but then later made visits in and out of the UK.
• The high and very high frequency move groups are substantially smaller than the low and medium groups.
• Initial work on these groups suggests there may be overlap between them which could be investigated by
looking at the impact of changing the boundaries and rules for each group.
• Standard visitor visas are the most common for these groups, and we believe these are likely to be a mix of
frequent visitors for business or family reasons, this may also include some very frequent holiday visitors.
• These people tend to make a large number of short visits on a regular basis. Current ONS assumption is
that some of these are highly skilled workers doing some form of regular permitted work in the UK.
Group Conditions / characteristics to be in
group
Number in
group
Patterns of movement within
group
Modal demographics
of group
High
frequency
• 20-29 journeys within 2 year period.
• Must have spent at least 6 months
outside the UK in the 2 year period.
15,000 • Avg length of stay in UK per
visit – 11 days.
• Avg length of stay outside
UK per visit – 18 days.
• Total Avg stay – 9 months.
• Visa – Standard
Visitor Visa
• Nationality – USA
• Age grp – 30-40
Very high
frequency
• 30+ journeys within 2 year period.
• Must have spent at least 6 months
outside the UK in the 2 year period.
12,000 • Avg length of stay in UK per
visit – 6 days.
• Avg length of stay outside
UK per visit – 9 days.
• Total Avg stay – 9 months.
• Visa – Standard
Visitor Visa
• Nationality – USA
• Age grp – 30-40

We can gain some insight into the nationality of the groups we have identified, and
compare these to all Exit Checks records for our period of interest. These charts show how
the top 10 most common nationalities of people in each group (right hand dots) compare to
the overall pattern of nationalities in all Exit Checks data we had (left hand dots).
While we know we are not capturing all circular movements, what we have captured gives an overview of some
groups who are making frequent or lengthy stays into / out of the UK. Further examination of these groups is
planned to better understand the patterns.
8
OVERALL LOW OVERALL MEDIUM
OVERALL HIGH OVERALL VERY HIGH

Our work on how we can group people and explore the circular patterns of
movement has led to a better understanding of how we might want to define
circular migration, as our work develops.
The Exit Checks data have shown that there are a variety of movement patterns and reasons for circulating.
Exit Checks is a good source for non-EEA circular patterns of movement, which merits more examination.
Our current assumptions (based on what the data have shown us):
• People who have a low or medium number of journeys, usually stay in the UK for periods of 2-5 months at
a time and travel for the purposes of study or family.
• People with a low and medium number of journeys will probably appear in current data sources, (e.g. MWS,
PDS) but these will not show their movement patterns.
• People who have a high or very high number of journeys, usually stay in the UK for a period of up to one
month at a time. We do not have any definitive reason for travel for this group, and are conducting further
research to understand them, and to try to identify business travellers.
• People with a high and very high number of journeys, who are resident in the UK, will most likely appear in
some data sources, but those who are not, may not appear in any.
Implications:
• There is no uniform way these people would be captured by current sources (some people may be
reporting short-term intentions, others long-term).
• Further sources need to be linked to the Exit Checks data to confirm assumptions around why people have
these circular patterns.

Putting administrative data at the core of our evidence on international migration (UK) and on
population (England and Wales) by 2020
It provides evidence for:
• Understanding concepts and definitions for migration
We have seen from this and previously published analysis of
Exit Checks data that many people are making multiple
journeys within a single period of leave to remain, and that the
people that we have observed with circular movement
patterns are not a homogenous group.
It is important for us to understand from these data what these
multiple journeys look like and the characteristics of people
making these circular journeys.
We also need to consider how we can include them into
definitions of long- or short-term migration, regular visitors or
new definitions that we could potentially use.
Further work is needed to understand what these circular
patterns of movement mean. Linking to other data will allow
us to understand patterns of activity inside the UK associated
with circular movement patterns and their impact on the
economy, housing, education and other public services.
The findings from this case study provide important insights
that will be key to the successful development of a population
and migration statistics system based on administrative data
sources.
Next steps
To continue research on circular patterns
of movement using linked data.
Our framework for transforming population
and migration statistics

• Further analysis looking at specific groups of people and understanding their
movement patterns over time, or for a specific year.
• Analysis to understand the impact of the rules we set around the borders between
groups, to ensure we are best describing useful and distinct groups.
• Investigate regional patterns and whether we can produce any estimates of
circular patterns of movement for the countries of the UK.
• Use other sources, such as RTI, to derive complementary indicators of circular
patterns of movement or activity. RTI will give coverage of EEA nationals,
addressing one of our major gaps.
• Link Exit Checks to other sources:
• Further Home Office data to identify similar circular movement patterns in
EEA nationals (who are not covered in our current extract).
• HESA – look further into our student circular patterns of movement, linking
with other work that is ongoing.
• MWS – to examine lags between arrival in the UK and registration, and MWS
arrival date.
• PAYE – see what jobs those engaged in circular movement patterns are
doing, if they are employed in the UK.
Recommendations and Next steps

Where are the gaps?
Covered Gaps
Geographical coverage Non-EEA nationals arriving/departing the UK
from all airports, some ferry ports and the
channel tunnel.
EEA nationals. Some
arrivals/departures via ferry and rail.
Travel occurring through the common
travel area.
Patterns of movement Arrivals and departures to/from the UK, occurring
between 08 April 2015 to 08 April 2018, for those
who held a non-visit visa at some point.
Arrivals before April 2015 and after
April 2018. Coverage of long-term
circular patterns of movement.
Sample excludes those solely on visit
visas during this period
Population of interest Non-EEA nationals who have held a non-visit
visa at some point during the time period
covered by our data.
EEA nationals are not captured by
Exit Checks.
UK citizens are not captured by Exit
Checks.
Non-EEA nationals who have only
held visit visas in our reference
period.1
We currently do not hold information
on the purpose of visit for many of the
identified group (based on visas
held).
(1) The extract of Exit Checks data we received only contained non-EEA nationals who had, at some point, held a non-
visit visa. The data did not include non-EEA nationals who had just held a visit visa.
Completing the picture

• Disclaimer: These research outputs on circular patterns of movement to and
from the UK are not official statistics.
• Rather, they are published as outputs from exploratory research to show users of
international migration statistics where we are on our transformation journey to put
administrative data at the core of our evidence on international migration (UK) and
on population (England and Wales) in 2020.
• These outputs must not be interpreted as an indicator of circular migration.
• These research outputs are based on experimental analysis of Exit Checks data.
We are still developing methods, therefore the numbers or proportions reported
here may change in future reporting on our journey to put administrative data at
the core of migration statistics.
• It is important that the information and research presented here be read alongside
the population and migration statistics transformation update report to aid
interpretation and avoid misunderstanding.
• These outputs must not be reproduced without this disclaimer and warning note.
Things you need to know

Contact Us
We would welcome your feedback on the exploratory research
presented here. Please get in touch at:
Email: pop.info@ons.gov.uk
Tel: 01329 444661

Further Links
Go back to: An update on our population and migration statistics transformation journey: A research
engagement report
Explore our other case studies on SlideShare
Transforming population and migration statistics: Administrative data-based population stocks and
flows
Transforming population and migration statistics: Emigration patterns of non-EU students
Transforming population and migration statistics: International student employment activity
Transforming population and migration statistics: Benefits and income activity patterns
Transforming population and migration statistics: NINo and NHS registration lags

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