Figures do Lie

 For decades, immigration statistics were based purely on a survey of people arriving and departing from UK air, sea and rail ports. Millions of passengers enter and leave the UK each year and picking migrants out of this enormous haystack has in part been a matter of luck. In the early 2010s, for example, these figures appeared to show an alarming situation where half of all international students were overstaying their visas. 

Under Theresa May, the Home Office launched a multi-pronged campaign to identify illegal immigrants, which included closing bogus colleges and introducing right-to-work and right-to-rent checks. New statistics in 2017 concluded the original overstaying estimate for students had simply been wrong, a fault of failing to count people properly – and a sign of how unreliable migration statistics were as a whole. There is no evidence of a major issue of non-EU students overstaying their entitlement to stay

But it was too late for one group that fell on the wrong side of the so-called hostile environment policies: people who had come legally from Commonwealth countries in the postwar era but couldn’t provide enough proof of this when questioned.

 These victims of the Windrush scandal suffered multiple injustices thanks to an imaginary foe in the numbers and a failure of government record-keeping.

From migration to railways, how bad data infiltrated British politics | Georgina Sturge | The Guardian