lonelyplanetmum
Your link at 05:51 also says this further down the page:
"These statistics should be taken with a considerable amount of salt."
"As I’ve been pointing out for some time, the ONS’s figures on net migration–people entering and leaving the country–are well out of line with the population statistics"
The author (Jonathan Portes) links to his previous article from June 2018;
Misunderestimating migration
voxeu.org/content/misunderestimating-migration
"According to the population estimates, the number of people born elsewhere in the EU and now resident in the UK increased by nearly 1.5 million over the eight years to mid-2017.That suggests that net migration of EU citizens to the UK over that period should have been a similar number. However, the migration statistics show cumulative net EU migration of only about 950,000."
"A very similar discrepancy–but in the opposite direction–applies to non-EU nationals.The IPS suggests total net migration of nearly 1.5 million, but the population estimates say that the number of people born outside the EU and resident in the UK has increased by less than 900,000.On the face of it, half a million people from outside the EU have vanished, but they’ve been replaced by about the same number of Europeans who we didn’t know we had."
"More likely is that one, or both, surveys is badly wrong.The obvious candidate is the IPS."
"It has long been obvious that it has been overestimating student net migration from outside the EU; it now seems likely that this has translated into an overestimate of non-EU migration overall."
"Meanwhile, it undercounted EU migration in the 2000s" "and I was arguing two years ago that the volume of National Insurance numbers being issued to EU citizens suggested their numbers were still being undercounted; this data seems to bear this out. Almost certainly, some EU citizens who arrive here thinking they’re only going to stay for a short time–and hence don’t tell the survey that they’re immigrants–end up staying.Nor is the APS immune to error–the number of people who are prepared to take the time to answer a very long list of questions has been shrinking, and maybe recent migrants are even more reluctant."
... "it does seem reasonably clear that in the recent past EU migration has been significantly higher, and non-EU migration significantly lower, than we thought."