My hon. Friend is absolutely right. As I said, the survey relies on full and frank answers from those being interviewed even to include them. If people say that they are just visiting a relative for a week, they are not counted as migrants. To that extent, the 70,000 range for potential error within the 95% confidence interval is of significant size for the estimate.
If annual immigration is 120,000 or 150,000, there is only a 5% or one in 20 chance that the official figures are on target. The figures could say that the Government are missing their net immigration target by tens of thousands when in fact they are meeting it, or they could show that the UK is meeting its target when in fact it is missing it by tens of thousands. We do not have enough confidence to know. It is clearly a completely inadequate measure of net migration, but we must be careful before dismissing it, because it is all we have.
That degree of confidence applies only to the headline numbers. The ONS estimate simply does not provide sufficient detail to judge properly the social and economic consequences of different types and origins of migration, and the effects of immigration policy on, for example, students or people from particular countries. Nor does it provide any useful idea about international migration in and out of local areas. Efforts to achieve a blunt net migration target are therefore bound to have unintended consequences, such as skills shortages and effects on universities.
The shortcomings of relying on the IPS were highlighted when the 2011 census showed that the population of England and Wales was 465,000 higher than expected
given the recorded number of births and deaths and the estimated level of net migration during the decade since the previous census. The ONS identified several possible causes for the difference but considered that the
“largest single cause is most likely to be underestimation of long-term immigration from central and eastern Europe in the middle part of the decade”,
which of course was not picked up by the international passenger survey. The ONS concluded that the underestimation came partly from taking samples of people from the wrong airports. That is, the IPS sample under-represented airports such as Cardiff and ports such as Newcastle, where more immigrants are coming in than was previously understood.
As a result, this April, the ONS published a revised set of net migration estimates for the United Kingdom for the period 2001 to 2011. Total net migration during that period is now estimated to have been 346,000 higher than previously thought; the original estimate of 2.18 million has been revised to 2.53 million, plus or minus 35,000.