We are going to have to fit another 10 million people in. So how do we make it nice for them – and for us? The new forecasts for population growth by the Office for National Statistics suggest that UK population will reach 73 million by 2037, a prospect that has been greeted with concern by some, and celebration by others. The concerns are about "our tiny crowded island", the celebration about the probability of becoming the most populous nation in Europe, for as we go up we are likely to pass Germany on the way down.
True, this demographic explosion may not take quite the charted course. Either or both of the two main drivers, a rising birth rate and inward migration, may ease off. It is possible, too, that rising longevity may stall. But the ONS forecasts are in line with those of other bodies, such as the United Nations, and anyone troubled by the outlook should think about the implications of a sharp fall in the birth rate, or the economic conditions that would reduce the attraction of the UK to migrants.
In any case, a considerable and sustained rise in population seems the only sensible assumption. So we have to consider how to make this work.
There are two broad issues, the physical and the societal. The first, on the face of it, looks daunting. England (and most of the growth will be in England) has just overtaken the Netherlands as the most densely populated country in Europe – we will leave Monaco aside for this particular calculation. London is past its post-war peak population and seems set to reach 10 million within the next 20 years. South-east England is already the largest agglomeration in Europe.
Yet, if you take other measures, the task seems more manageable. London has roughly half the population density of Paris, and that is not a bad place to live. Densities are much lower than Hong Kong or Singapore. It ought to be possible to house a somewhat larger population without destroying countryside, and to house people rather better than we do with the little boxes we are building at the moment. People need to move around and have places to work; their children need to be educated; we will need more medical services and so on.
All this needs investment. But the growth generated by these additions to our workforce will also generate the funds for that investment. The issue is really whether the present debate about big projects, such as HS2 or Heathrow expansion, takes into account the needs and aspirations of that extra 10 million people.
There is an economic concept called opportunity cost – what you cannot do with the resources you have available because you are committing these to a project. See HS2 in that light – what other projects could be built instead – and you have to wonder whether this is really the highest priority for this growing population.
The physical issues of a population of 73 million, however, are straightforward when set against the social and political changes that are likely to follow – political in the widest sense. One obvious outcome is that the country will become even more cosmopolitan, with the sort of changes that are evident in London spreading outwards across the land. Politicians will have to accommodate the needs and aspirations of a differently balanced electorate. I don't think many politicians appreciate quite how difficult it will be to represent an electorate that is quite different from the electorate of their experience or background.
There is a further issue here. The balance of power will shift within Britain, with in all probability the South increasing its weight even further, for that is likely to see the largest increases in population. It is even wider than this. Britain's place in Europe will change if it becomes its most populous country, and probably its largest economy. It is obviously an economic issue, but is also a political one. If Europe's biggest economy were outside the EU in 20 years' time (and I don't think the forthcoming referendum will be the last word on the matter), that would not only affect the whole continent.
Look at it this way. In most of Europe, population will be declining. It will feel more like Japan now. That is not necessarily a catastrophe, for Japan manages to give a calm, secure and satisfying lifestyle to the majority of its people. But a Britain with a more diverse and still-growing population will come to feel more like the United States. It already feels something of a halfway house, anchored in mid-Atlantic. The age profile of a country affects its attitudes, aspirations and ideas. The UK will continue to age, in the sense that the numbers of over-65s will rise as a proportion of the population, but it will age much more slowly than the rest of Europe.
The big point here is that, insofar as anything is certain in this world, this surge in population will happen. We do not have a choice, for it can be affected only at the margins. Therefore we have to think through, in a straightforward and practical way, how we can manage it. We have to try to turn it to the advantage of all of our people for, in this at least, we are indeed all in it together – and rather closely packed.