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Round numbers and records: What do headline statistics tell us about migration?

25 Aug 2015

This Thursday, the Office for National Statistics will publish a new set of migration statistics. The data will cover many different topics, but two numbers are likely to attract attention: one relating to the ‘flow’ of migrants in and out of the UK, the other relating to the ‘stock’ of foreign-born people living in the UK.

The ‘flow’ number is the latest net migration data. In the last quarter’s data, net migration was estimated to stand at 318,000 – just 2,000 below the highest level previous recorded in 2005, shortly after the accession of the A8 countries to the EU. This is the figure that is used to assess the government’s target to reduce net migration “from the hundreds of thousands to then tens of thousands”. It could go down in Thursday’s data, or it could go up and break the previous record.

The second is the number of UK residents in 2014 who were born abroad. This number has increased steadily over time, and the current trend suggests that it is likely to exceed 8 million for the first time in 2014 (Figure 1).

Figure 1

Round numbers and record figures always attract attention. But what do they actually mean? Do these numbers have an inherent importance in themselves?

One thing worth bearing in mind when thinking about the meaning of these numbers is that both are estimates. They have margins of error and appear in the public domain with a lag, which means that we don’t always know precisely when specific landmark numbers are hit. For example, the ONS estimated last quarter’s net migration level at 318,000 plus or minus 44,000, because the survey on which the numbers are based is small and therefore not particularly precise. If the reported number had been 4,000 higher and had thus slightly exceeded the previous 320,000 record, it might have made a bigger news story but from a statistical perspective the number would be virtually the same.

Similarly, while the UK’s foreign-born population is expected to exceed 8 million for the first time in the published ONS data, the official statistics take some time to produce, which means that this threshold is actually likely to have been crossed more than a year ago.

In other words, ‘landmark’ moments at which statistical measures reach a certain point are often somewhat arbitrary.

What are the consequences of rising migration?

Even if the statistics come with caveats, of course, the basic message that migration now is higher than it was a few years ago is still valid.

The biggest challenge interpreting these numbers is that there is no optimum size for the UK’s population or for the number of migrants who live here. From an economic perspective, immigration brings both costs and benefits and affects different people in different ways, leaving no objective method of deciding what the ‘right number’ of  migrants is. Different demographic, economic and political arguments can be marshalled in favour of either increasing or reducing immigration, and reasonable people will disagree.

David Cameron has described UK population growth as ‘unsustainable’ and in 2012 parliament voted to support a non-binding motion that immigration policies should be used to prevent the UK population from exceeding 70 million. By contrast, the Scottish government has an objective of increasing population growth, arguing that rural and coastal communities are not sustainable without it.

Looking at public opinion, polls regularly find that members of the UK public feel there are ‘too many’ migrants in the UK. The proportion of British people concerned about the number of migrants in the country has been broadly consistent for decades, however, and was substantial even during the 1990s when estimated levels of net migration were relatively low. Immigration has become more salient in the eyes of the public over the last 20 years. In August this year, Ipsos Mori’s Issues Index poll recorded the highest ever level of concern about immigration, with 50% citing it as one of the most important issues facing the country. But public opinion data does not provide a clear guide to what the ‘right’ level of migration would be, making it hard to identify an optimal number of migrants from a democratic perspective, either.

By way of context, the share of the UK population that was born abroad is comparable to that of the other EU-15 countries (countries that were members of the EU before 2004). In 2014, six of these countries had larger foreign-born shares of the population, including Austria, Ireland and Sweden, while eight had smaller shares, including Italy, Portugal and Finland (Figure 2). The prevalence of migration in the UK is therefore by no means unprecedented by European standards. Economic performance and attitudes to migration in those countries have varied widely in recent years and their relationship with immigration numbers is far from straightforward.

Figure 2

Seeing the wood for the trees

When new migration numbers are released, they are often used as a simple metric of the government’s success or failure in managing migration. This has particularly been the case since the 100,000 net migration target was introduced.

These headline statistics can be interesting, but they only provide the narrowest slice of the story. They tell us little about either the positive or negative impacts of migration or the trade-offs involved in policy decisions that affect the numbers. The more fundamental questions about policy successes and failures are more nuanced. They include how immigration affects the UK labour market, whether it makes existing UK residents wealthier, how different groups of newcomers are integrating, how immigration is perceived in local communities, and how policies at the local and national level affect the impacts of immigration and the UK’s ability to accommodate the levels of migration it receives.

These things are harder to convey in a single number.

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