To warn about the consequences of an exodus of European Union workers from the British economy probably comes across like shouting fire in the midst of Noah’s flood.
Aren’t there more than two million EU nationals in the British workforce, double the number a decade ago?
Isn’t net immigration from the EU running at almost 200,000 a year according to the latest figures?
Didn’t millions of Britons vote for Brexit precisely to reduce the numbers of workers from the Continent coming to Britain?
Yet if we know that when the flood waters recede there will be an abundance of vulnerable dry kindling and a scorching sun, it’s not alarmist to warn of the risk of a conflagration.
And we do know that.
The size of the UK-born workforce appears to have peaked in 2015 at around 26.5 million.
Workforce participation rates are at a record high.
This implies that any net increase in demand for employees from firms, over the coming decade at least, will probably have to be met by new migrants.
Think of all those additional care workers to look after the burgeoning population of elderly.
Think of those new doctors and nurses to staff packed surgeries and overstretched wards.
Think of construction workers to build the new homes pretty much everyone now agrees we desperately need.
Think of the software developers, research scientists, engineers and myriad other skilled workers that Britain will require to drive our national productivity and increase our living standards.
We can – and should – certainly fill some of these skilled vacancies through retraining the existing UK workforce.
But not all of them can be filled in this way.
Moreover, this is to cut the labour force cake differently. To make the cake bigger, we will almost certainly need to import labour from abroad.
But what if the labour doesn’t want to come?
The latest figures from the Office for National Statistics this week suggested the number of EU-born workers in the UK workforce may also have now peaked at 2.3 million.
There are other signs that net immigration from the EU is now in decline.
Employers are starting to complain of labour shortages.
The migration expert from King’s College London, Jonathan Portes, has predicted a sharp fall in EU migration rates in the coming years for a variety reasons.
The assumption among British politicians is that EU migration post-Brexit will be like a tap that can be turned on and off.
They will import any new workers we genuinely need, they will “manage” migration, they will “take back control”.
But what if the tap is turned and no water comes out? What if there is a supply problem?
The UK atmosphere towards immigrants has hardly been welcoming over the past year.
There was spike in violence directed at European migrants in the wake of the Brexit vote.
The uncertainty over the future rights and status of EU nationals who have made their home here has created anxiety, heartache and anger.
The tone in the most influential organs of the national print media is unrelentingly hysterical and hostile.
Senior politicians have misrepresented the scientific evidence on immigration’s impact on living standards.
Others have ignored it out of sheer cowardice, scared of making themselves targets of the right-wing press or of going against what they perceive to be the popular mood.
Would it really be surprising if a skilled European worker, or even an unskilled one, faced with a choice about taking a job in Britain and somewhere else on the Continent or around the world, gave us a miss given the repellent tone of our public discourse on migration and the insouciant attitude of our politicians?
The assumption is that Britain can choose immigrants.
But one day, and possibly quite soon, we might wake up to the hard reality that immigrants can also choose Britain.
And then we may have cause for deep regret over the way that we have allowed the national conversation about immigrants to unfold.
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