The free movement of people within the EU is unpopular with some Brits. Indeed, it is the main argument used by UKIP for pulling out of the EU. But free movement is good for our economy. It also enriches our culture and gives our own citizens more opportunities to work, study and retire across the Channel. There are 2.2 million Brits living in the rest of the EU, and 2.3 million citizens from other EU countries living here.
If we left the EU, it is not at all clear what would happen to our citizens living and working abroad. But the best guess is that tit-for-tat would prevail. In the unlikely event that relations got really acrimonious and we kicked EU citizens out of the UK, the EU would probably retaliate and kick out our citizens too. That would be disastrous. More likely, we would just severely curtail new immigrants crossing the Channel to Britain. But if the EU then stopped Brits going to live and work there, that would still be a diminution of the freedom we currently enjoy.
Now look at the EU citizens living in the UK. Most are young and skilled. They come here mainly to work. Their so-called "non-activity" rate - which covers pensioners, students and stay-at-home parents as well as the unemployed - is 30%. The rate for the UK population as a whole is 43%. Meanwhile, 32% of recent arrivals have university degrees compared to 21% of the native population.
The average age of the European immigrant population in Britain was 34 in 2011, compared with 41 for the native population. We don't pay much for the immigrants' education since they normally arrive after being educated. And, since most of them are working age, we don't pay much for their pensions or health care either. Many eventually return home, carrying good memories of the UK with them.
Many Brits are worried about EU immigrants taking our benefits and our jobs. The facts, though, don't bear this out. European immigrants are half as likely as natives to receive state benefits or tax credits, according to a study by academics at University College London.
EU citizens haven't been taking "our jobs" either. The UK economy has been good at creating jobs. Three million were created between 1997 and 2012. But British citizens have often lacked the skills and incentives to grab these opportunities. Immigration from the rest of the EU and further afield has filled the gap.
Think of the National Health Service, caring for old people or the hospitality industry. Many immigrants take more naturally to these jobs than Brits. If we left the EU and EU citizens were no longer allowed to work here, these services would suffer.
Of course, too many young Brits are unemployed. But the solution is to train them up and encourage them to take jobs rather than live off welfare - not to prevent other EU citizens coming here. As Boris Johnson, the mayor of London, put it in 2013: "We need to help our young - not beat up on Johnny Foreigner."
Indeed, the ability of companies to employ hard-working foreigners from across the Channel is actually creating jobs because it has improved the competitiveness of British companies by helping them to expand, and by encouraging foreigners to set up businesses here too. Indeed, immigrants are almost twice as likely as native Brits to be entrepreneurs. Rather than pulling up the drawbridge, we should be rolling out the red carpet.
This is an excerpt from Hugo Dixon's new book - The In/Out Question: Why Britain should stay in the EU and fight to make it better. Available here for £1.99