Britain’s Office for National Statistics (ONS) has admitted its own figures underestimated long-term migration between 2009 and 2016 by almost a quarter of a million.
The statistical agency discovered the error after examining Department for Work and Pensions (DWP) data and comparing it to their own estimates based on the International Passenger Survey (IPS), according to The Times.
Britons are often surprised to learn that the country’s migration statistics are not measured by counting people in and out of the country and monitoring their length of stay etc., but through a clipboard-based survey originally devised in the 1960s to guesstimatetourism and business travel trends.
A relatively small number of people — measured in thousands, while the number of people entering and leaving the United Kingdom is in the hundreds of millions — are approached at a relatively small number of entry points to Britain, at certain times of day, and asked for information about where they come from, why they are coming, and how long they intend to stay, with the ONS extrapolating its immigration statistics from the answers they receive.