Patrick Pearse believed that our island could support 30 million people or more. Is the objective of a much higher population desirable though? Are the recent terrorist attacks in London not a consequence of an overcrowded country?

In 1851, the population of the 26 counties that comprise the Republic was, even after the calamitous fall resulting from the Famine, still almost one-quarter of that of the UK (excluding those counties).

If the Irish population had grown since then at the same rate as the UK population, it would now be more than 15 million people, three times the actual population.

Irish population levels will be largely determined by future migration levels

The population, in absolute terms, declined continuously between 1851 and 1921, at a time when the UK population doubled. Fifty years later, in 1971, there had been no increase in the Irish population, compared with a further large increase in the UK population. This in a sense was the greatest policy failure of the first 50 years of an independent Ireland.

This downward trend began to be reversed in the mid-1970s, and especially in the last 25 years, with the Irish population as a share of the UK population back at levels not seen since the 1910s.

Where now for Irish population levels? That will be largely determined by future migration levels. Without any net migration there will be a steady, but slow population increase given fairly constant birth and death rates. With large net immigration flows, it could increase rapidly or not increase at all if net emigration resumes.

Ageing population

A related concern is the projected significant ageing of the population over the next 30 years, bringing with it dependency issues not seen since the 1950s, with consequential effects on public and private finances.

Clearly the country could accommodate say a twofold increase in population, to almost 10 million, and still have far fewer people per square kilometre than, for example, England, Germany or the Netherlands.

More important than the land mass though is the state of infrastructural and public services such as roads, health, housing and education, to accommodate any increase in net immigration.

The failure to provide more public services, paid for out of the taxes collected from immigrants, rather than immigration per se, was and is the root cause of many of the problems with immigration in England in recent years.

This shifting of the blame for overcrowding in English cities from wilful decreases in funding on public services to immigrants has been exposed in the recent Grenfell Tower fire disaster.

Clearly the immigrants can benefit hugely from moving, as why otherwise would they migrate here? For the same reasons as Irish people migrated to the New World in the second half of the 19th-century, or to the UK in the 20th-century.

There is little evidence also to suggest that migrants, from the European Union in particular, push down wages or displace the jobs of domestic workers. They in fact often fill key gaps in the jobs market, for example in the health service or the hospitality and IT sectors. This is a lesson that has been brought home forcefully in the last few months in Britain.

Most studies show that migrants contribute much more to the public purse than they extract from it. As alluded to already, the failure then is not providing the necessary increased public services and infrastructure resulting from immigration rather than immigration per se.

Planning

Cities are densely-populated places, by definition. But if well-planned and -funded there is really no such thing as an optimal city size. One can have much better services and lifestyle in many large cities than in small towns. This is why so many people migrate to them. And many of the people migrating to cities come anyway from within a country.

Migrants could redress the ageing population situation that lies ahead for Ireland. They could also provide much of the healthcare personnel needed to accommodate a changing population structure.

It is not the density that matters with regard to population size but proper planning

There must of course be strict rules applied to migration inflows from outside the EU as otherwise the country could be overwhelmed, with large net negative economic effects.

However, one has to be careful that this argument, as the Economist argued recently, is not used simply “to provide an economic basis for a cultural prejudice; what may be a natural human proclivity to feel more comfortable surrounded by people who look and talk the same”.

One must remember also that, in the past, arguments on similar grounds were expressed against the immigration of Irish people to Britain and the US. We should not forget our history, above all in this regard.

It is not the density that matters with regard to population size but proper planning in terms of the provision of public infrastructure and services. For which immigrants will usually have paid for in full, and more, out of taxation.

John O’Hagan is professor emeritus of economics at TCD