It is common knowledge that immigration is the key issue in every general election. Every party participating must have a clear policy on this sensitive subject. In 2010, as part of the election manifesto, it was announced by then leader of the Conservative party David Cameron that his party was seeking to reduce net migration to ‘tens of thousands’. The announcement was made following the accession of Bulgaria and Romania, also known as the A2 countries, to the EU in 2007, and despite the fact that at the time there were restrictions in place imposed by the government that prevented nationals of these countries from fully accessing the UK labour market, and that the figure referred to did not include migration from the EU, tensions in relation to the ever-increasing number of migrants coming into this country were running high. Looking back, there is no doubt that reducing the number of migrants was never expected to take effect to the dramatic extent promised, but rather the pledge itself was a political move designed to woo the voters and thus help the Conservative party to take office. In 2015, the part of the manifesto relating to net migration figures stayed the same, although it had been obvious over the years that the reality was that the number previously announced and relied on in the previous election campaign was not even close to the target, and that the trend in migration was the opposite.

In a surprise move by the current Prime Minister Theresa May to announce the snap general election that is to take place on 8 June, she is continuing to rely on the erstwhile pledge of her party to reduce net migration to ‘tens of thousands’ as part of her current election campaign. It is clear that the issue has become extremely politicised over the years, and the fact that the pledge has been impossible to fulfil is irrelevant. However, if one is to look at the origins of the figure in question, it may come as a surprise that the data used for it has been coming from an unreliable source: the International Passenger Survey (IPS). The IPS is a tourism survey, and it has been collecting information about passengers entering and leaving the UK since 1961. The information comprises data gathered from various ports of entry into the country, such as airports and sea ports as well as Eurostar terminals and Eurotunnel shuttle train services. The survey was not designed for counting migration figures in the first place, but has been used for that purpose, as the UK does not require migrants to register after entering the country. As part of the survey, the number of interviews conducted by border officials ranges from 700,000 to 800,000 each year, with about 250,000 being used to produce estimates in relation to long-term migration and tourism. The data on net migration is estimated by identifying number of people assumed to be travelling for the purpose of long-term migration. This leads to a significant level of uncertainty as to the accuracy of the figures inferred, which in turn is an indication that the figures have proved themselves to be remarkably unreliable. At the moment, there is no other method available to calculate net migration figures. In 2015, airlines were ordered to provide information on passengers leaving the country, though this has had little effect on calculating the number of people migrating, as data obtained has had no connection to Home Office data on visas.

It is worth noting that the rhetoric about controlling the number of migrants has slowed down following the vote to leave the EU last year. It is remarkable, though, how such a number as the net migration figure, which is being obtained in such an approximate way, can play such a role in forming public opinion.