In the 1950s and 1960s, black Americans moved into the middle classes at a rate not experienced before or since. When seen though the lens of 1967, it would have been logical to foresee the American black future as a middle-class one, as represented by The Cosby Show, Toni Morrison and Condoleezza Rice. Yet it did not turn out like that.

At some time in the 1980s, the mass upward social mobility of blacks stopped.

Why was this? Why did the self-confident black civil rights movement, characterised by intelligent, peaceful protest and justified moral superiority, spawn the nihilism, boorishness and misogyny of 50 Cent?

One of the many reasons advanced to explain this development has been immigration. There appears to be a direct correlation between immigration and black social advancement. When US immigration is low, black people do well economically; the converse is true when immigration is high.

Black Americans did very well in the 1950s and early 1960s when immigrants accounted for just 8 per cent of the increase in the US labour force – an historically low figure. Contrast this with immigrants accounting for 55 per cent of the growth in the labour force in the first decade of the century and more than 27 per cent in the 1990s.

By the 1980s and 1990s, competition for blue-collar jobs had increased dramatically as new immigrants flooded into the US again. Two things happened: blacks disproportionately lost out to the new immigrants, and blue-collar wages fell, while professional incomes rose.

While there is little argument that immigration has been beneficial for the US economy and society as a whole, it is clear that the middle class has done better than the working class. Is there anything we can learn in Ireland from this experience?

Will the same happen here?

The history of immigration is the history of social fluidity. In a fascinating book entitled How the Irish Became White, author Noel Ignatiev traces the evolution of the Irish in America and how we eventually changed colour in the eyes of the Anglo Saxon establishment.

Initially, the Irish were seen as untermensch by the white Anglo-Saxon Protestant (Wasp) establishment, but that changed in the late 19th century. Going back to the famine, Ignatiev explains how waves of immigrants from Ireland displaced the American black labourers with alarming speed, by undercutting them in a classic example of 19th century outsourcing.

As is the case today, outsourcing created much discussion in the editorial pages. Here is an extract from a letter in the Philadelphia Daily Sun newspaper in 1849:

�There is direct competition between the blacks and the Irish as we all know.

�The wharfs and new building attest to this fact; when a few years ago we saw none but blacks, we now see nothing but Irish.�

Not only did the Irish replace the blacks but, having replaced them, we set up a powerful trade union movement based on race to make sure that we kept them out. Economic history is replete with other examples of the dislocating nature of immigration.

This brings us to the issue of Irish Ferries. The overriding lesson from this tawdry tale is that immigration will hurt some of us and enrich others. Junior Cert economics tells us immigration will ultimately drive down the wages of Irish workers in areas where they have to compete with Polish, Lithuanian or Slovakian immigrants.

This process will benefit professional Irish people who will profit greatly from the fall in the costs of services provided by tradesmen, seamen, cleaners, security men and home helps, to mention but a few occupations.

A topical area that highlights this process is childcare. In recent years, we have seen an explosion in the number of foreign nannies and au pairs. Had they not come here, childcare would be even more expensive and many thousands of educated Irish women would find it impossible – or, more pointedly, uneconomic � to go out to work. But both problems were solved by immigrants.

An article in US magazine The Atlantic, by Caitlin Flanagan, stated that �for many young mothers, the precise intersection of their two most passionate influences – their profound, almost physical love for their children and their fervent wish to make something of themselves beyond the hall door – is the exact spot where the foreign worker turns up for work each day’�.

So who benefits? Obviously, the professional Irishwoman and the immigrant woman. But what about the Irishwoman who used to look after other people’s children? Her wage has been compressed downwards to a level where it would not have been had there been no immigrants.

For many, this might be positive, if they can get better-paid jobs, which is possible while the boom continues.

So as long as there are jobs aplenty, the disproportionate impact of immigration on working-class Irish people will be masked. However, if that were to change – as the ESRI hinted in its latest report – what might happen?

An indicator of what could happen politically in Ireland can be seen in the French EU referendum earlier this year.

The unsung hero of the French �Non’ campaign was the demonised �Polish plumber’.

The invasion of Polish plumbers was seen as emblematic of the problem with the EU. If it weren’t for enlargement, there wouldn’t be half as many Polish plumbers who were coming to France, competing with French tradesmen and driving down the wages of blue-collar workers across the country.

But apart from the Polish worker, his family in Katowice and second-hand car salesmen in suburban Lyon, who benefits from this? Well, the white-collar, bureaucratic elite of Paris and other metropolitan centres who buy the now-cheaper services of plumbers.

This divergence in who gains from immigration and who is threatened caused blue-collar France to vote overwhelmingly against the EU constitution. In contrast, white-collar France voted for it.

So could this happen here? Until now, Irish trade unions have been on the side of the immigrants and championed foreign workers in the few areas where blatant exploitation has been uncovered. The booming capitalist economy has, ironically, allowed international workers’ solidarity to flourish.

However, Irish Ferries has focused attention on the big issue, which is that the interests of the foreign worker and the Irish worker are not the same, particularly if the foreign worker is prepared to undercut the local lad.

This implies that the next big battle for the unions will be not against Irish capitalists, but against foreign workers. Already, Siptu has begun to employ Polish-speaking organisers to try to co-opt Polish workers into the union movement, but will this be enough? The experience of black Americans over the years suggests not. It remains to be seen whether international worker solidarity can survive the impact of a slowing economy. Let’s hope it doesn’t get too messy.