In general, smaller countries can thrive in a world with free trade. Many of the countries with the highest incomes per head have small populations – countries like Luxembourg, Singapore, Denmark and Norway.

In that fundamental sense, Britain does not ‘need’ migration. It has a population of 67 million, and considerable reserves of unused labour.

Of course, as the population increases, the economy may benefit from a bigger talent pool and greater specialisation. But to the extent that population growth is seen as desirable, the resulting benefits must be weighed against the future costs that a larger population will impose on land, housing, services and infrastructure.

England, after all, is three times as dense as France and two and half times as dense as Germany.

A larger workforce will certainly make the economy bigger, but it will not raise living standards unless it makes GDP (the quantity of goods and services) grow more rapidly than the labour force.

What matters to the existing population is not GDP for its own sake, but GDP per head.

Economic benefits from immigration unquestionably exist. But beyond a certain point, the benefits do not rise in proportion to the numbers settling here, whereas the problems (and costs) do.

In a densely populated city like London, for example, rapid population growth puts immense strain on housing, services, roads and public transport, while increasing the cost of land and housing. The British taxpayer will often have to bear the cost: either through higher taxes or hidden subsides such as those to make accommodation more affordable for key workers.

The adaptations required by mass immigration are so large that the required investment will have to be planned so far in advance that new facilities become available at the time they are needed.

Unfortunately, the changes required to accommodate a rapidly growing population may be both difficult and costly to implement, even when problems have become too severe to ignore.

As Professor Robert Rowthorn has noted: “Suitable land may not be available except at great material or environmental cost. Re-engineering existing cities to accommodate the additional population may be very costly, and expansion into the surrounding countryside may be resisted by local people.”

This is incorrect.

Based on research commissioned by the Migration Advisory Committee, immigrants overall paid £4.3bn less in tax than what they took out in benefits and services (2016/17). The report concluded that different types of immigration have differing effects.

Earlier research bore similar results: they show that the impact of immigration is small (less than +1% of GDP) or negative (less than -1% of GDP). In short, the positive tax contribution of some migrants is largely or wholly offset by the negative tax contribution of others. High earners pay more in taxes than they receive in services from the state, while less well-off people pay less in tax than they draw out.

The age-structure of the British population is made slightly more youthful by immigration. But that cannot solve the pensions problem, since immigrants grow old too – and those arriving now will retire when the ‘dependency ratio’ (the current ratio between working age and retired people) is far worse.

It is often said that British businesses need foreign workers to fill labour shortages. But since we imported over a million migrant workers to fill more than a million vacancies… we have created as many vacancies again.

This is not a coincidence. Importing foreign workers to fill labour shortages is a self-defeating policy, since immigrants spend their wages on food and clothing and other necessities that have to be produced by other people. Each person creates work for others, so the amount of work that needs doing is potentially infinite.

What is really meant by this are jobs no British person wants to do at a particular wage.

In general, immigrants who arrive from poorer countries have lower salary expectations than those of the British workforce, since their point of comparison is underpaid people from back home. This is the reason why big business and its agents of opinion are without exception supporters of more open borders.

Under an ideal immigration system (i.e., limited numbers of skilled migrants), employers will have to pay British workers higher wages to compensate for the unpleasantness of a job.

Productivity, vital to the economy, may be enhanced by immigrants moving into well-paid jobs that are in demand. This is most obvious in the case of skilled professionals – people who work in technology, finance, law, and medicine.

Unfortunately, this is the only category of migrant that open border advocates want you to notice. Today, immigrant workers are overrepresented in low- and semi-skilled professions in the hospitality, transport and storage sectors. Their presence in Britain is good for private companies who get to employ cheap, non-unionised labour. But it tends to be bad for the native poor by holding down their wages.

In the long run such jobs cannot be sustained at acceptable living standards without welfare. Immigration of the unskilled may also distort the economy and create dependency. For example, letting businesses import skills which Britons could themselves acquire undermines the incentive of employers to train and upskill the British workforce. It may also disincentivise companies from investing in new technology – or from switching to the production of less labour-intensive commodities.

The result: low-wage, low-productivity, low-skill enterprises flourish.

Some of our institutions, which are indeed the best in the world, benefit hugely from the enrolment of foreign students. No one who works in a university can be unaware of that.

On the other hand, many foreign students who arrive in the UK do not enrol at a top university. According to Home Secretary Suella Braverman, too many foreign students “[prop] up, frankly, substandard courses in inadequate institutions.”

Moreover, many of the ‘dependants’ (partners and children) who accompany these students are economically inactive and pay less in tax than what they consume in public services, such as schools and hospitals. For example, in 2022 the number of Nigerian dependants (67,000) exceeded the number of Nigerian students enrolled at university (58,000).

The accumulated knowledge from decades of research implies that ethnic diversity may have a negative impact on the economy and society if it leads to lower trust and poor communication between individuals – for example, because of language barriers or cultural differences.

In the south east of England and around the Pennine towns in the north, in particular, there are places where people from different ethnic origins never meet, never talk, and never go into each other’s homes.

Without a stable population there cannot be the values, habits, understandings and loyalties that enable us to live as we do and perhaps sometimes to act for the benefit of others in less fortunate places.