Net Weight: Focusing only on net migration doesn't show the whole picture.

The suite of information in today’s quarterly migration figures from the Office for National Statistics (ONS) tells us some interesting things – long-term net migration continues to increase, emigration has declined and there has been a substantial rise in immigration of both students and migrants from the former Eastern European nations that joined the EU in 2004 (A8 countries).

But the current focus of the public debate about these statistics is the latest figures for long-term net migration, which the government is aiming to reduce to the tens of thousands by the end of parliament.

But this creates a profound problem for public debate and immigration policy: focusing only on long-term net migration - the level of immigration minus emigration of people who intend to migrate for at least one year – risks failing to consider other vital data about migration in the UK – not least, how many migrants are actually here.

There are, of course, many ways that one can pick apart the UK’s migration figures - as outlined in the Migration Observatory’s report on the Top 10 Problems in the Evidence Base for Immigration in the UK. ONS figures on emigration, immigration and, by extension, net migration are based on survey data that are subject to considerable margins of error. For example, in 2009 emigration was estimated to be between 315,800 and 359,100, a range of over 43,000. 

In addition to this there are substantial differences in the level and changes of net migration suggested by different ONS data sources – in 2009 the Long Term International Migration (LTIM) estimates for net migration of non-British citizens were 242,000 (only slightly lower than the 2008 figure) while the change in the stock of non-British residents based on Annual Population Survey (APS) figures was 175,000 (significantly lower than the 2008 figure).These two data sources measure slightly different aspects of migration but this large discrepancy has not yet been fully explained.

So, we can conclude from this that there is a substantial level of uncertainty about what the actual net migration figures really are. But even if this problem were overcome by a radical improvement in the data there would still be an inescapable issue – on its own net migration does not tell us the whole story about changes to migration and the migrant population in the UK.

The overall net migration figure used in public debate and by government to define and measure its policy target includes migration of British citizens and excludes short-term migrants (defined as those planning to stay/leave for less than one year).

Consequently, even if the UK manages to achieve lower or even negative long-term net migration (a hypothetical scenario), it doesn’t mean that there will be a corresponding reduction in the growth of the total migrant population (including short-term migrants). If the reduction in long-term net migration is accompanied by an increase in short-term migration, the growth in the stock of migrants in the UK may not change - it may even increase.

We may well see the number of short-term migrants in the UK rise in the near future. For example, recent changes to Tier 1 and 2 mean that people who have entered the UK through intra-company transfers who wish to stay for longer than one year must meet a minimum salary threshold of £40,000 per year – but those staying for less than a year can be paid £24,000 to £40,000. It would not be surprising to see a significant increase in the number of intra-company transfers who come to work in the UK for just under a year.

Changes in overall net migration also may mislead by combining British, EU, and non-EU migration into a single figure. Reductions in overall net migration may be accompanied by increases in the net migration of non-British migrants. If more British citizens leave the UK, and assuming nothing else changes, this would lower overall net migration, but leave the number of non-British migrants entering and staying in the UK unaffected. By the same token, reductions in non-British immigration may be masked by reductions in British emigration.

Net migration also ignores actual immigration numbers – there is no difference in net migration terms between emigration of 1,000,000 people with immigration of 1,000,001 (net migration of +1) and emigration of one person with immigration of two (net migration +1). But this ignores the fact that a high turnover of people in a country has significant consequences for a wide range of public policy issues.

So it is clear that net migration figures alone are an inadequate tool for building a realistic understanding of the changing scale of migration and migrants in the UK – an issue that clearly is of significant concern to the public. 

That is not to say that long-term net migration should not be a key indicator that should be part of the public debate and policy-making, but it is only one indicator, and as such fails to capture a range of other potentially important changes to migration and migrants in the UK. To provide a more complete picture we would need to monitor a range of indicators that include, at a minimum, information about levels and changes to:

  • The stock of migrants in the UK
  • Long-term immigration flows
  • Long-term net migration flows
  • Short-term migration flows

Each indicator should be available separately for British, other EU and non-EU migrants.

By having a suite of different indicators, public debate could be based on a better understanding of how migration is changing in the UK, and what impact various policy changes are really having on migrant numbers.

In policy terms, moving away from a narrow focus on net migration towards a more nuanced and comprehensive set of indicators will help avoid unintended consequences and, in the end, make policy more evidence based.