For England and Wales, the mid-2011 estimate of short-term immigrants based on the International Passenger Survey (IPS) was 41,000 higher than the 2011 Census estimate of short-term residents (STRs).
Six main differences were identified between the two sets of estimates; these differences relate to how the two sources define short-term immigrants and how the estimates are produced.
The two sources appear to categorise short-term immigrants differently; the IPS estimated fewer short-term immigrants visiting for work and study and more short-term immigrants visiting for reasons other than work or study compared to the 2011 Census.
The distribution of short-term immigrant workers and students to local authorities in England and Wales is similar to the distribution of STR workers and students to local authorities in the 2011 Census.
This report examines two similar data sets on short term migration: estimates of short-term immigration for local authorities and England and Wales and estimates of short-term residents (STRs) from the 2011 Census. These two datasets differ in terms of definitions and the estimates produced and this report aims to help the user understand these differences.
Mid-year short-term international immigration estimates using administrative data sources were published for the first time in February 2012 as experimental statistics. The recent release of data on STRs from the 2011 Census provides an independent, high quality data source that can be compared to these estimates. The benefits of using the Census are that it is high quality, provides a complete coverage of non-UK born STRs in England and Wales and has not been used in the production of the Office for National Statistics (ONS) short-term immigration estimates.
There are a number of administrative data sources that record short-term migrants in England and Wales but they cannot be used in comparisons with the ONS estimates for two reasons. Firstly, although these administrative sources contain some short-term migrants, they do not offer a complete coverage of the short-term migrant population in England and Wales. For example the Migrant Worker Scan1 is an administrative data source that identifies short-term migrant workers but does not include short-term migrants who come to England and Wales for reasons other than work. Secondly, most of the administrative sources that contain short-term migrants have been used by ONS for the development of the short-term immigration estimates for local authorities. A research report (1.18 Mb Pdf) including the methodology used to produce the short-term immigration estimates for local authorities is available on the ONS website.
The work presented here focuses on the mid-year short-term immigration estimates for local authorities in England and Wales; however comparisons are also made for regional and country level estimates also produced by ONS. The report begins by providing some background information on the short-term migration estimates. It then goes on to consider the definitional differences between these estimates and estimates of STRs from the 2011 Census so that users of migration statistics can understand some of the differences that result from the comparison. This is followed by comparisons at each geographic level.
The Migrant Worker Scan is an extract of the National Insurance Recording System and holds information on all adult overseas nationals who register for a National Insurance Number in the UK.
England and Wales level short-term migration statistics are published by the ONS as official statistics following an assessment by the UK Statistics Authority in 2012. They are available from 2004, and the latest publication refers to the year ending mid-2011.They are produced using data from the International Passenger Survey (IPS)1. These data are collected from interviews that take place at the end of the short-term migrant’s visit. As is the case with all sample surveys, the estimates produced from the IPS are based upon one of a number of samples that could have been drawn during the interview period. This means that there is a degree of variability around the estimates produced.
Estimates of short-term immigration for local authorities in England and Wales using the current methodology were published for the first time in February 2012 as experimental statistics. In March 2013, they were designated as National Statistics. A copy of the report “Assessment of compliance with the Code of Practice for Official Statistics on Short-term International Immigration for England and Wales” is available on the UK Statistics Authority website.
While the England and Wales estimates are produced directly from the IPS data, the local authority estimates are based on a distributional model that uses administrative data sources to distribute the England and Wales short-term immigration estimates down to local authority level. Short-term immigration estimates for local authorities are available for the years ending mid-2008 to mid-2011. The latest estimates (the year ending mid-2011) were published on 23 May 2013.
The 2011 Census is the first census of England and Wales to produce outputs relating to short-term immigrants. The 2011 Census defined these immigrants as ‘short-term residents’ because the data represent the stock of short-term migrants in England and Wales at a particular point in time (those present on 27 March 2011).
The Census team developed the Coverage Assessment and Adjustment methodology (126.3 Kb Pdf) to address the problem of undercounting both usual residents and short-term residents. The methodology used standard statistical techniques to measure the level of undercount in the Census and provide an assessment of the characteristics of individuals and households missed. Hence the Census short-term resident estimates include those that are estimated to be present but who did not respond to the Census. This approach means that the Census figures are the best possible estimates of the population. However, because they are based in part on a sample survey (the Census Coverage Survey (CSS)), they are estimates rather than counts, and are subject to sampling error. The level of error is dependent on a number of factors including the CCS sample size, the size of the population and the census response rate.
There were less complete item responses to the Census question on short-term residents compared to the other questions in the Census. This will have some impact on the quality of the estimates of the short-term residents when compared to the Census estimates of the usually resident2 population of England and Wales. For short-term residents in England and Wales intending to stay three to six months and six to twelve months, the response rates were 73 % and 81 % respectively. These response rates for short-term residents (2.78 Mb Excel sheet) were lower than the response rate for the usual resident population, which was 94 per cent.
Information on the quality of the International Passenger Survey in relation to international migration (324.8 Kb Pdf) flows is available on the ONS website. More detailed information on the International Passenger Survey methodology and coverage can be found at Appendix C of the annual publication Travel Trends.
A ‘usual resident’ of the UK for 2011 Census purposes, is anyone who, on census day 2011, was in the UK and had stayed or intended to stay in the UK for a period of 12 months or more, or had a permanent UK address and was outside the UK and intended to be outside the UK for less than 12 months. Visitors and short-term residents (who enter or leave the UK for less than 12 months) are included in the enumeration but not in the estimates of the usually resident population.
Although both the 2011 Census and the IPS provide a full coverage of short-term immigrants across England and Wales, there are some differences in how each source defines short-term migrants. These differences need to be taken into account when comparisons are made.
The Census refers to short-term immigrants as short-term residents (STRs). A census STR is anyone born outside of the UK who, on Census day (27 March 2011) was in the UK and had stayed or intended to stay in the UK for a period of three months or more but less than 12 months.
The IPS identifies short-term migrants by their flow. Flow is described as the direction of travel of the visitor combined with whether they are a foreign resident1 or a UK resident. A short-term migrant inflow (immigrant) is defined in the IPS as a foreign resident who visited the UK and stayed for a period of three months or more but less than 12 months. Estimates are also produced at England and Wales level for lengths of stay between one and 12 months. Estimates of flow include short-term migrants regardless of their country of birth and will include UK born migrants.
Both sets of estimates (mid-year and Census) as defined above, are available for England and Wales, English regions and Wales, and local authorities in England and Wales. The mid-year national short-term migration estimates include migrants who come to England and Wales for any reason while the mid-year local authority level estimates include immigrants who come only for work or study. The Census estimates of STRs include migrants who come to England and Wales for any reason at both national and sub-national level.
Short-term migration outflows (a UK resident who v isited an overseas country and stayed for a period of three months or more but less than 12 months) are available from the IPS but only for England and Wales and are not the focus of this report. The latest (mid-2011) IPS-based short-term migration estimates for England and Wales are available on the ONS website.
There are six main differences that arise from the above definitions and are illustrated in Infographics 2 and 3. These differences are:
The time reference period is not the same. The mid-year short-term immigration estimates presented in this report are for short-term migrants who arrived in the period from 1 July 2010 to 30 June 2011 and are the most recent data available. The 2011 Census includes all STRs who were present on Census day and could have arrived sometime in the previous 12 months. Infographic 1 shows the months and year of arrival that each estimate covers. The infographic shows that the overlap between the 2011 Census and the mid-2011 estimate is nine months.
The data collection methods are different. Short-term migration estimates from the IPS are based on a sample of face to face interviews that are conducted throughout the year at UK ports. The Census STR estimate is based on a census taken at a particular point in time. Therefore, the Census does not count STRs who arrived after Census day or STRs who arrived in the year up to 27th March 2011 but left before Census day. This may mean that the Census does not include short-term residents who live in the UK for summer seasonal work.
The population coverage is not exactly the same. The Census only captures those STRs who are foreign-born (non-UK born) and who were physically in the country on Census day, whereas the IPS includes both non-UK and UK-born overseas short-term migrants who stay in the UK for 3 to 12 months.
The mid-year short-term migration estimates considered in this report are flows while the Census STR estimates are stocks. The IPS records the number of visits, not the number of visitors. This means that those entering or leaving England and Wales more than once in a mid-year to mid-year period are counted on each visit. The Census estimate is the stock of STRs who were present in England and Wales on Census day. Estimates of mid-year short-term migration stocks are produced at England and Wales level and are published on the ONS website.
There is a difference between intention and actual behaviour. The IPS interview of overseas short-term migrants who visit the UK takes place at the end of the migrant’s visit when factual information about visit duration is available. This is more complete and reliable than the information collected at the beginning of a migrant’s visit when the migrant states their intentions regarding length of stay. The 2011 Census used the following question to identify short-term residents:
“Including the time that you have already spent here, how long do you intend to stay in the United Kingdom?"
This question asks about the intentions of a migrant and does not record their actual behaviour as the IPS does. This means that the Census estimate will include short-term resident switchers2, as migrants may change their intentions and stay for more than 12 months in the UK (and this way becoming usual residents) or less than three months (and this way becoming visitors). It could also miss long-term migrant switchers3 or visitor switchers4 as people intending to stay for more than 12 months or less than 3 months may change their intentions and stay for three to 12 months (and this way becoming short-term residents).
Both the 2011 Census and the IPS categorise short-term migrants into three broad categories – workers, students and others. This categorisation is based on the migrant’s economic activity. The two sources collect information on economic activity differently. The IPS asks the main reason that motivated the respondent to travel to the UK and this reason is given by the respondent. The 2011 Census asked respondents what was their economic activity during the last week. Any temporary or casual work done by a short-term resident in the last week would classify them as a worker. Many short-term immigrants arrive in the UK for reasons other than work or study but then take some form of work or enrol on short courses. These short-term immigrants are classified as others in the IPS but they appear as workers or students on the Census if they had engaged in such activity in the last week.
The definition of residence as used by IPS is living in a country (the country in which he or she has a place to live, where he or she normally spends the daily period of rest) for 12 months or more.
Short-term resident switchers are those who intended to stay in the UK for between three to 12 months but changed their intentions and stayed longer than 12 months or less than 3 months.
Long-term migrant switchers are those who intended to stay in the UK for more than 12 months but changed their intentions and stayed for between three and 12 months.
Visitor switchers are those who intended to stay in the UK for less than three months but changed their intentions and stayed for between three and 12 months.
According to the 2011 Census (146 Kb Excel sheet) there were 195,000 short-term residents (STRs) staying in England and Wales on Census day. According to data from the International Passenger Survey (IPS), for the year ending mid-2011, an estimated 236,000 short-term migrants visited England and Wales, for any purpose for between three and 12 months, which is around 41,000 more than the 2011 Census estimate of STRs. There are a number of reasons why these two estimates will be different and these were outlined in Section 3. In particular, the Census estimate is a stock of foreign born migrants at one point in time and would be expected to be lower than the mid-year estimate which includes all in-flows over the course of a year for both UK and non UK born migrants.
Estimates of mid-year short-term migrant stocks have also been produced from the IPS by calculating an average number of migrants in the country during one year based on the individual flows. For example, if four migrants each stayed in England and Wales for three months, this would be equivalent to one person staying for one year and so the stock count would be one. For the year ending mid-2011, the IPS based short-term migrant stock estimate was 97,000. This is 98,000 lower than the Census estimate. These differences may be due in part to the way that the two sets of stocks have been estimated, particularly the IPS method which converts flows to stocks.
In this section, the estimates are considered at England and Wales level and are summarised in Table 1 below.
|2011 Census STR||%||IPS mid-2011 ST immigrants||%|
|65 and over||6,000||3||24,000||10|
Figure 1 shows the total estimate from each source split by reason for visit (based on economic activity). Although the two estimates are comparable as totals, they consist of different types of migrants. The IPS based estimate has fewer students and workers but more ‘other’ migrants than the 2011 Census. Students are the biggest category in the 2011 Census STR estimates and are around 36,000 more than the short-term immigrant student estimate in the IPS. The category ‘other’ includes short-term migrants whose main reason for visit was neither work nor study. It includes people who come to visit friends and family or people who come for extended holidays or business trips. For the year ending mid-2011, the IPS estimated three times more short-term immigrants in the ‘other’ category than the 2011 Census.
This comparison suggests that the IPS and Census identify the economic activity of short-term immigrants differently and this could be explained by the different data collection methods. As only the main reason for visit is recorded in the IPS, this group will include immigrants whose main reason for visit may fall into the ‘other’ category but may also work or study during their stay. Some of these immigrants may be categorised as coming for ‘study’ or ‘work’ according to the Census which asks what their activity was in the previous week.
Figure 2 shows the England and Wales estimates from each source split by nationality1. The 2011 Census STR estimate for UK nationals was 12,000 lower than the mid-2011 IPS estimate since the Census did not include UK born STRs (who usually hold a British passport). Middle East and Asia was the subcontinent with the highest estimate for both the Census and the IPS. For the European Union (EU) member countries that joined the EU between April 2001 and March 2011 (see background note 2), the Census estimated 19,000 fewer short-term residents than the IPS. This group of nationalities has the biggest difference between the two sources.
In IPS and Census terms, nationality is defined as the country which supplied an individual’s passport.
The regional short-term immigration estimates published by ONS are based on the United Nations definition of a short-term immigrant; overseas residents who migrate to the UK for three to 12 months for work or study purposes. The regional totals are produced by summing the estimates of the local authorities that constitute each region. Regional and local authority data for short-term residents (STRs) who visited for reasons other than work or study are available only from the 2011 Census and are not the focus of this report. The regional analysis that follows considers short-term students and workers separately.
Figure 3 compares the 2011 Census STR workers with the mid-2011 short-term immigrant workers by region. The two sources show similar estimates for each region with London receiving the most short-term workers. London is also the region with the biggest difference between the two sources. At England and Wales level, the number of STR workers in the Census was around 15,000 more than in the IPS. Since London boroughs attract the majority of short-term migrant workers, the difference for London is more pronounced than for the other regions.
It should be noted that short-term immigrants captured by the IPS whose main reason for visit is ‘other’ are not included in these comparisons. Many of these ‘other’ short-term immigrants could be categorised as short-term resident workers in the Census if they take up some form of employment during their stay.
Figure 4 compares the 2011 Census STR students with the mid-2011 short-term immigrant students by region. The 2011 Census shows more STR students in every region compared with the mid-2011 estimates. At England and Wales level the number of STR students in the Census was around 36,000 more than the mid-2011 short-term immigrant student estimate. This difference is distributed equally across the regions, which suggests that although the IPS may have estimated fewer short-term immigrant students, the methodology used for the regional distribution is not biased towards one or more regions in England and Wales.
It should be noted that short-term immigrants captured in the IPS whose main reason for visit is ‘other’ are not included in these comparisons. Many of these ‘other’ short-term immigrants could be categorised as short-term resident students in the Census if they take up some form of study during their stay.
The mid-year local authority short-term immigration estimates published by ONS are based on the United Nations definition of a short-term immigrant which is overseas residents who migrate to the UK for three to 12 months for work or study purposes. This definition is used because the administrative sources that are currently available and are used for distributing to local authorities, are unlikely to include short-term migrants that stay less than three months or migrate for reasons other than work or study (for example holiday makers or those visiting family and friends). The ONS currently produces only short-term immigration estimates for local authorities. Short-term emigration estimates at local authority level are not available because there are currently no suitable data, either in the form of a Census, survey or administrative register that can be used to produce them.
As previously mentioned, administrative data sources are used to distribute the IPS totals of worker and student immigrants to local authorities in England and Wales. An initial validation of the mid-year local authority short-term immigration estimates can be found in a report published in February 2012 and is available on the ONS website (1.18 Mb Pdf) .
Figures 5 to 8 provide an overview of the differences between the two estimates. An extract of the Census estimate for students and workers, excluding migrants who were not working or studying, has been used for the following analysis. This allows for more meaningful comparisons with the mid-year short-term immigration estimates which are produced for students and workers only. Figures 5 and 6 show the differences between the 2011 Census short-term resident (STR) and the mid-2011 short-term immigration estimates for all local authorities in England and Wales. For the majority of local authorities (226 out of 348), the 2011 Census estimated more STRs than the mid-2011 short-term migration estimates. There are 118 local authorities where the mid-2011 estimate is larger than the 2011 Census. These differences are shown in the S-shaped curve in Figure 5. Overall, as shown in Figure 6, the differences for most of the local authorities (227) are small, and range between -100 and 100 immigrants.
Figure 7 shows the 20 local authorities in England and Wales with the largest difference between the 2011 Census STR and the mid-2011 short-term immigrants, split by workers and students. All of the top 20 local authorities have positive differences which means that the 2011 Census estimated more STRs than the mid-2011 estimate. Most of the local authorities in the top 20 are areas that attract large numbers of students and it is the student estimate that makes up most of the difference. This is because the 2011 Census estimated approximately 36,000 more STR students than the IPS. For the local authority of Kensington and Chelsea, the opposite can be seen as it is the workers that make up the majority of the difference. Workers also account for a large part of the difference in the local authorities of Westminster, Southwark and Tower Hamlets.
The difference in the overall estimate of short-term migrant students between the two sources can be explained in part by the fact that some of the short-term migrants captured in the IPS whose main reason for visit was ‘other’ (who are not included in this comparison) may also have been studying and could have been categorised as a short-term resident student in the Census.
Table 2 shows the 20 local authorities with the largest estimate of STRs in the 2011 Census and where they ranked in the mid-2011 short-term immigration estimates. Westminster is ranked first in the 2011 Census and second in the mid-2011 estimates. As it can be seen from Table 2, 14 out of the 20 local authorities, appear in the top 20 of both sources. The absolute difference between the two sets of estimates is large in some cases, as illustrated in Figure 7, although this will be due in part to the differences in the way the economic activity and reason for visit are recorded in the two sources.
|Local Authority||Region||2011 Census Ranking||Mid-2011 Ranking|
|Nottingham UA||East Midlands||6||11|
|Leeds||Yorkshire and The Humber||10||25|
|Sheffield||Yorkshire and The Humber||12||7|
|Newcastle upon Tyne||North East||13||13|
|Cambridge||East of England||14||12|
|Kensington and Chelsea||London||15||42|
|Brighton and Hove UA||South East||20||23|
Table 3 shows the top 20 local authorities according to the mid-2011 short-term immigration estimates. Newham is ranked first according to the mid-2011 estimates but according to the 2011 Census estimate is ranked 11th.
|Local Authority||Region||Mid-2011 Ranking||2011 Census Ranking|
|Sheffield||Yorkshire and The Humber||7||12|
|Nottingham UA||East Midlands||11||6|
|Cambridge||East of England||12||14|
|Newcastle upon Tyne||North East||13||13|
A correlation analysis has been carried out between the ranked 2011 Census STRs and the ranked mid-2011 immigration estimates and is shown in Figure 8. Ranked data have been used in place of the actual estimates to determine whether the mid-2011 short-term immigrants are distributed to the same local authorities as the 2011 Census STRs. The correlation coefficient between the ranked Census and ranked IPS data is 0.88 which means that there is a strong positive association between the rankings of the two sources. This suggests that the two sources give a similar geographical distribution.
As the mid-year short-term immigration estimates continue to be produced and time series develops, there will be a better understanding of the local distributions that they are based upon. These distributions use a number of administrative data sources (see background note 3), the quality of which will vary year by year. Over time, it will be possible to see how these distributions behave and the effect the administrative sources have on them.
The 2011 Census is the first census that estimated the short-term resident (STR) population of England and Wales. This report considers these data on STRs collected by the 2011 Census and the mid-2011 short-term migration estimates. There are a number of differences in the way the two sources (Census and International Passenger Survey) define short-term immigration as well as in the methods used to produce the estimates. These definitional differences mean that there are differences between the two sets of estimates.
The mid-2011 IPS-based estimate of short-term immigrants was 41,000 greater than the 2011 Census estimate of STRs. The different definitions used by the two sources can account for some of this difference. For example the mid-year estimates include short-term migrants who are UK born and are not included in the 2011 Census estimates. In addition, the Census short-term residents are an estimate of a stock at Census day (27 March 2011) which means that short-term migrants who left England and Wales before Census day were not counted but appear in the mid-year estimates. Also, the mid-year estimate reflects actual behaviour rather than intention of an immigrant and this will have some impact on the Census estimate of STRs as some immigrants may stay longer or shorter than intended.
The two sources appear to categorise short-term migrants differently as the IPS captured many more short-term immigrants visiting for ‘other’ reasons and fewer short-term immigrants visiting for work or study compared to the 2011 Census. Some of the short-term immigrants visiting for ‘other’ reasons in the IPS may have also worked or studied and could have been included as short-term students or workers in the Census which records the activity of the migrant the week before Census day rather than main reason for visit.
At the regional and local level, short-term migrants stating ‘other’ as their main reason for visit are not included and so it is not surprising that there are some differences between the two sets of estimates at local level. Consequently, while most areas had relatively small differences, larger differences were seen in some areas such as London boroughs and university cities which tend to attract short term migrant students and workers. The high correlation of the ranked estimates provides evidence that the methodology used to distribute the mid-year short term immigration estimates for workers and students is comparable to the distribution of STRs in the Census. As the estimates continue to be produced, a better understanding will be gained of the distributions and the underlying administrative data sources and how effectively they capture short-term immigrants.
Feedback from people who use the mid-2011 estimates will help to understand the estimates further. If you would like to provide feedback, please send it to the email address below.
ONS also publishes estimates of long-term international immigration but there is no overlap between short-term and long-term migrants as long-term migration refers to moves that last more than a year. The combined short-term and long-term immigration estimates can provide users with a more complete picture of international immigration for England and Wales. The latest data and publications on long-term international migration are available on the ONS website.
Some short-term immigrants are also included in the travel and tourism statistics published by ONS. However, these two series of statistics are not comparable as travel and tourism statistics are based on visits (for any purpose) of less than twelve months’ duration.
Short-term immigrants coming to England and Wales stay for less than a year and therefore they are not part of the resident population as presented in the ONS annual population estimates statistical bulletin. The latest release of the annual mid-year population estimates is available on the ONS website.
EU Member Countries (March 2001): The countries that have joined the European Union up to March 2001 (also known as EU15) are Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Netherlands, Portugal, Spain, Sweden, and UK.
EU Member Countries (April 2001 - March 2011): The countries that have joined the European Union between April 2001 and March 2011 (also known as EU12) are Bulgaria Cyprus, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Romania, Slovakia, and Slovenia.
The administrative data sources used to distribute the IPS short-term immigrant workers to local authorities in England and Wales are:
A8 workers (Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Slovakia, and Slovenia): Migrant Worker Scan, A8 subset
A2 workers (Bulgaria and Romania): Migrant Worker Scan, A2 subset
Rest of European Economic Area (EEA) workers: Migrant Worker Scan, Rest of EEA subset
Non-EEA workers: Grants of visa extensions and Certificates of Sponsorship to work
The administrative sources used to distribute the IPS short-term immigrant students to local authorities in England and Wales are:
Higher Education students: Higher Education Statistics Agency Student Record
Further Education students from EEA countries studying in England: Individual Learner Record (Business, Innovation and Skills)
Further Education students from EEA countries studying in Wales: Lifelong Learning Wales Record (Welsh Government)
Further Education students from non-EEA countries: Grants of visa extensions and Certificates of Acceptance to study
Details of the policy governing the release of new data are available by visiting www.statisticsauthority.gov.uk/assessment/code-of-practice/index.html or from the Media Relations Office email: email@example.com
These National Statistics are produced to high professional standards and released according to the arrangements approved by the UK Statistics Authority.
ONS (December 2011) ‘2011 Census: Census response, return and coverage rates’, available at: http://www.ons.gov.uk/ons/guide-method/census/2011/census-data/2011-census-data/2011-first-release/first-release--quality-assurance-and-methodology-papers/census-response-rates.xls (2.78 Mb Excel sheet)
ONS (September 2012) ‘2011 Census: Number of non-UK short-term residents by broad age group and sex, unrounded estimates, England and Wales and constituent countries’, available at: http://www.ons.gov.uk/ons/rel/census/2011-census/population-and-household-estimates-for-england-and-wales---unrounded-figures-for-the-data-published-16-july-2012/rft-1-2-ew-mm01.xls (146 Kb Excel sheet)
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UK Statistics Authority (April 2013) ‘Statistics on Short-term International Migration for England and Wales – Assessment of Compliance with the Code of Practice for Official Statistics’, available at: http://www.statisticsauthority.gov.uk/assessment/assessment/assessment-reports/assessment-report-247---statistics-on-short-term-international-migration-for-england-and-wales.pdf
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ONS (October 2009) ‘Research Report on Local Authority level Short-term Migration Estimates’, available at: http://www.ons.gov.uk/ons/guide-method/method-quality/imps/updates-and-reports/historical/2009/research-report-on-local-authority-level-short-term-migration-estimates---october-2009.pdf (1.37 Mb Pdf)
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ONS (February 2012) ‘Distributing Short-term Migrants to Local Authorities’, available at: http://www.ons.gov.uk/ons/guide-method/method-quality/imps/updates-and-reports/current-updates-and-releases/distributing-short-term-migrants-to-local-authorities/research-report--distributing-short-term-migrants-to-local-authorities.pdf (1.37 Mb Pdf)
United Nations (1998) ‘Recommendations on Statistics of International Migration, Revision 1, Statistical Papers Series M, No. 58, Rev. 1, available at: http://unstats.un.org/unsd/publication/SeriesM/SeriesM_58rev1E.pdf