1. Background

In the year ending September 2016, we saw a statistically significant decrease in the number of non-EU citizens coming to the UK. This decrease was being driven by fewer people coming to study. However, over the same period, the number of study visas issued to non-European Economic Area nationals increased by 2%. In the February 2017 Migration Statistics Quarterly Report (MSQR), we highlighted this notable difference to users and outlined the differences between these data sources that could have accounted for the differing trends. We noted that we would continue to monitor this trend and draw comparisons with other data sources. For the following three quarters (May 2017, August 2017, November 2017) we continued to highlight to users that the decreases we were seeing in these estimates reflected the decrease from the year ending September data, that did not align with Home Office visa data.

In the year ending September 2017, we saw an increase in the number of non-EU citizens coming to the UK. Again, this was driven by more people coming to study. In February 2018’s MSQR we highlighted to users that interpretations of this increase should be made with caution, due to the drop in the previous year’s estimates. We encouraged users to look at the longer-term trends, instead of the year on year change.

In May 2018, we carried out an independent International Passenger Survey (IPS) assurance review. This highlighted that the IPS is more susceptible to sampling variability for students, as most students arrive at the start of the academic year in Quarter 3 (July to Sept) creating a cluster effect. In September 2016, we believe the IPS sample missed students which led to the unusual drop in the non-EU study estimate.

In light of the IPS assurance review findings and our increased understanding of administrative data from our transformation programme, in the July MSQR we began to transform the way we present migration statistics to our users. We provided our best assessment of what is happening to international migration based on all available data sources.

For non-EU students, we compared IPS, Home Office student visa data and Higher Education Statistics Agency (HESA) enrolment data. As such, we produced an illustrative revised IPS trend (Figure 1) – to demonstrate that if the IPS continued to increase at the same rate as the visa data – we would not have seen the unexpected drop in the non-EU study estimates in 2016 to 2017.

Figure 1: Non-EU long-term student immigration trends by data source with illustrative adjustment, UK, year ending June 2018

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Our best assessment, using all available data sources is that non-EU long-term student immigration has remained relatively stable over the past few years.

In November 2018, we informed our users via the MSQR and the accompanying notes in our data tables that we would review this illustrative adjustment and consider making a formal adjustment.

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2. What is being revised?

The Office for National Statistics (ONS) is transforming the way we produce population and migration statistics, to better meet the needs of our users. Working in partnership across the Government Statistical Service (GSS), we are progressing a programme of work to put administrative data at the core of our evidence on international migration in the UK.

This revision is to address an isolated sampling issue with the data of non-EU students in Quarter 3 (July to Sept) 2016.

The revised estimates have superseded the original estimates in the latest quarterly provisional long-term international migration estimates spreadsheet. There are no confidence intervals for the revised figures, as it is not possible to quantify the uncertainty associated with them.

No revisions have been made to the Non-EU country groupings (Asia, Rest of World) and they will therefore not sum to the revised non-EU estimates.

The effect of this revision on estimates – for the years ending September 2016, December 2016, March 2017 and June 2017 – is an increase of approximately 33,000 and can be seen in Tables 1 to 4.

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3. What is not being revised?

EU migration

Part of our transformation journey is to better understand patterns of student migration. We are not revising estimates of EU immigration for study for the following reasons:

The International Passenger Survey (IPS) data for EU students are more variable than non-EU over a longer time-period. The EU estimates have a less apparent drop in Quarter 3 (July to Sept) 2016 as the numbers are smaller. The variability in the EU student estimates over time needs further investigation as part of our ongoing transformation programme.

There are coverage and definitional differences between the IPS and the most comparable data sources – Higher Education Statistics Agency (HESA) and Universities and Colleges Admissions Service (UCAS).

The most comparable data sources for EU students – HESA and UCAS – show differing trends in the most recent data.

Annual 2016 migration tables

Annually in November we publish our final annual Long-Term International Migration (LTIM), International Passenger Survey (IPS) and methodology tables. These tables contain several other variables, besides those featured in the quarterly provisional spreadsheet. The revision will not be applied to these tables, as we do not have adequate data to reliably revise the more granular breakdowns by all variables, for example Country of Birth, Sex and Route.

We have added guidance to these tables to advise users that the headline figures (immigration, net migration) in the final 2016 annual tables will not match the revised figures in the quarterly provisional spreadsheet.

Emigration of former student immigrants

We are not revising estimates of emigration of former immigrants for formal study. As we continue to improve our understanding of administrative data, our future reporting will aim to integrate evidence from further sources, where appropriate.

Non-EU country groupings

No revisions have been made to the Non-EU country groupings (Asia, Rest of World) and they will therefore not sum to the revised non-EU estimates in the quarterly provisional spreadsheet.

International Passenger Survey estimates by individual quarter

We have not revised the estimate for Quarter 3 (July to Sept) 2016 because these estimates by quarter are not as robust as our estimates for rolling years and are not official statistics.

Mid-year population estimates

The Office for National Statistics (ONS) Centre for Ageing and Demography are not revising the mid-year population estimates (MYE) for mid-2017 because:

  • the impact would be less than 0.05% (adding approximately 33,000 more people to the usually resident population of the UK); the confidence interval around the MYE is around +/- 0.2% and this change is not materially significant

  • the unavailability of more granular geographical breakdowns of the data required for the MYE processing

  • the impact a revision has on stakeholders and the recency of the last set of revised population estimates

For more information relating to the MYEs, please see the mid-year population estimates quality and methodology information.

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4. Methodology

We explored several data sources which could potentially be used to adjust the year ending (YE) September 2016 International Passenger Survey (IPS) estimate of non-EU study.

These data sources measure different groups of students therefore they are not directly comparable, as demonstrated in Table 5. However, we do expect to see some concurrence in the trends between these data sources, as the concepts they measure are similar.

The trends of these data sources for EU and non-EU students (before this revision) can be seen in the Annex.

Of the data sources we considered, visas are most comparable with our non-EU IPS study estimates because:

  • visas are granted to non-EU nationals

  • visas are granted for all levels of formal study (further and higher education)

  • the length of a visa (greater than one year) can be used as a proxy for long-term length of stay in the UK which more closely aligns with the UN definition of a long-term migrant

  • being granted a visa shows a strong intention to come to the UK to study

We know there was an isolated sampling issue during the collection of data on international students in the IPS in Quarter 3 (July to Sept) 2016. This revision assumes that the change in non-EU long-term student visas issued is a reasonable proxy for the change in non-EU student immigration for that quarter. Based on the current data sources available to us and the trends they show (see Annex), the Office for National Statistics (ONS) Centre for International Migration and Methods Research and Data division are confident with this assumption.

This revision proportionally increases the YE September 2016 IPS estimate by the same amount as the year on year visa percentage change, which adds approximately 33,000 more non-EU students to our estimate. These additional students are then “fed through” into the subsequent estimates and three rolling years as seen in Tables 1 to 4.

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5. Annex

Figure 2: Non-EU long-term student immigration trends by data source, UK, year ending September 2018

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Figure 3: EU long-term student immigration trends by data source, UK, year ending September 2018

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Contact details for this Methodology

Ann Blake
Telephone: +44 (0)1329 44 4097