Who are buying all the new houses?

No, it isn't. And the fallacy in the argument can be seen if we pretend it's not about immigrants, but about new babies. Do you need more and more new babies to shore up an ever-expanding population? No, you don't.

What we're talking about here is the dependency ratio: the number of people who are working/producing in the country versus the total number of people in the country. Obviously, the people who are not working/producing have to be maintained, directly or indirectly, by those who are. The people who are not working/producing largely consist of the young, the elderly and the sick/infirm. (If the economy is badly organised or inefficient or in recession you can add to that the people who could work and would like to work, but can't get work. And you can also add people who are legally or socially discouraged from working, or from working as productively as they could — e.g., in the past, married women.)

So. If the birthrate falls, then all other things being equal 20—25 years later the number of people entering the workforce will fall. The number of people leaving the workforce at that time won't fall so the overall workforce will fall, and the dependency ratio will get worse. Each worker will have to support more non-workers than used to be the case.

What can you do about this? Well, if you foresee the problem you can adopt measures to discourage a fall in the birthrate in the first place, but (a) it's too late for that now; you should have done it 20 years ago, plus (b) evidence suggests that it's actually very difficult to influence the birthrate through social policies. (That needn't stop you trying, but you would be wise to have a plan B.)

You can discourage people from leaving the workforce through raising the pension age or cutting retirement benefits. Obviously, that's very unpopular, and therefore politically difficult.

If you have sufficient foresight you can save during the "fat years" when the workforce is still large — you put a share of taxes/national income into investment funds that you will draw on to sustain the non-workers when the workforce shrinks. Again, if the workforce is shrinking now, or will do very soon, it's too late to do this.

Or, you can grow the workforce by encouraging immigration of working-age people. This is in fact a very effective way of dealing with the problem, both because it can work more or less immediately and because, in the long run, it's actually more effective than new babies are — a new baby initially makes matters worse, because it adds to the non-working age population for the first 20-25 years of its life. The immigrant has spent the corresponding period of his life in another country, being maintained by that country's workforce.

But - and this is the key — you don't have to encourage immigration without limit; only so much as is necessary to give you the dependency ratio that you think is optimal. For the reason just pointed out, this actually means fewer than the number of new babies you would have needed to achieve the optimal dependency ratio. And, at the other end, when those immigrants retire, yes, they'll add to the dependency ratio, but so would the new babies when they reached retirement age. And you don't need more immigrants to sustain the dependency ratio unless you've had an inadequate birthrate all along. In which case, you would have needed more immigrants anyway.

By and large, if your birthrate is low the only way to avoid immigration without increasing the birthrate is to accept a declining population, declining productivity and declining living standards, relative to similar countries that have higher birthrates or receive migrants (or both). Examples of where precisely this is happening right now include Japan, Greece, Bulgaria, Russia and Italy. Countries where they have low birthrates but this isn't happening, partly because they encourage immigration to maintain productivity, include Sweden, Switzerland, Germany and Singapore.

Ireland from the 1920s to the 1950s is an interesting case. Obviously, we had a high birthrate, but we still had a declining population, and in particular a declining working-age population, because of very high emigration. So the expected consequence - rising dependency ratio; falling productivity; relative decline in living standards - did indeed ensue. We addressed that with economic policies that attracted investment, created job opportunities and therefore reduced emigration. It worked — the Irish dependency ratio fell steadily from the 1950s until 2010, since when it has been rising again.

I was addressing your claim that . .

You keep needing more and more immigrants to shore up an ever expanding population

I disagree with that claim. I think it's wrong, for the reasons stated.

You are now asking an entirely different question:

Do you agree with immigration at current levels, year on year ? Or not?

The question seems a little unrealistic, since there's no obvious reason why the 2025 level of immigration should continue year on year, indefinitely, and on the whole it seems unlikely that it will — immigration figures have fluctuated in the past; they are likely to do so in the future.

So, I think the strict answer is — I don't agree with immigration at current levels, year on year, both in the sense that I don't think there will be immigration at current levels, year on year, and in the sense that I have no particular reason to think that it would be desirable for that to happen.

There was a report there a couple of weeks ago on the average number of properties owned by landlords in Ireland. Apparently, there's something like 122 landlords who each own more than 100 properties, making up something like 27% of the entire market. That's a serious problem.

Why? Because 122 landlords run over a quarter of the rental market. That's not a good thing.