Thank you, Mr Walker, for the opportunity to present to the House the Select Committee on Public Administration’s report of the 2013-14 Session on migration statistics. It has proved one of the most controversial that we have produced during this Parliament.
Migration statistics are of supreme importance to public policy and the debate about immigration in this country. National and local government depend on those estimates in planning public services. For reasons of security, we need to know not only how many people are arriving in and leaving the UK, but who they are. Migration statistics help us understand what is happening in British society and the British economy.
Accurate and reliable migration statistics are also important for public trust. How can the public trust politicians’ promises on immigration if we do not have reliable numbers on which to base our policies? One reason why the debate on immigration has become so toxic is that people no longer believe they are being told the truth; they do not even believe that Governments understand what is happening to their own country.
We conducted our inquiry last year and came to a conclusion that everybody in the know about immigration has understood for years, but been loth to say too clearly for fear of the consequences: the immigration statistics produced by the Office for National Statistics and the Home Office are but blunt instruments for measuring, managing and understanding migration to and from the UK, and they are not fit for purpose.
The current sources of migration statistics were established when migration levels were much lower than they are today. Those sources are not adequate for understanding the scale and complexity of modern migration flows, despite attempts in recent years to improve their accuracy and usefulness. Most people are astonished when they learn how the inadequate estimates that we do have are compiled. When a person checks in or out of the country, their passport is scanned, but they are not counted in or out of the country, even if they are a foreign national. The headline immigration, emigration and net migration numbers are annual estimates based on interviews of about 800,000 people stopped at random at ports and airports each year—a tiny fraction of the overall flow of passengers and people in and out of the UK. The method is called the international passenger survey.
The number of non-UK citizens identified from the sample as migrants entering or leaving the UK each year is fewer than 5,000. Most of the numbers that we
hear in the immigration debate are based on that tiny sample of people, many of whom might be reticent, to say the least, about giving full and frank answers about where they have come from, who they are, why they are here and where they are going. To be clear, that group includes people entering and emigrating from the UK, so the sample number of immigrants in the survey may be as small as 3,000.
Unsurprisingly, migration estimates based on the international passenger survey are subject to a large margin of error, known to statisticians as the confidence interval: that is, the degree of confidence that it is possible to have about a particular margin of error. As we all know, the Government have stated that they intend to bring net migration—the difference between annual immigration into and emigration out of the UK—down from hundreds of thousands to tens of thousands. That is not a 90% cut; in fact, it amounts to about 50%.
On the ONS calculations for net migration as measured by the unadjusted IPS estimate, the 95% confidence interval is plus or minus 35,000, meaning that we can only be 95% certain that the true figure lies within 35,000 of the estimate either way. In other words, the error range is 70,000.