08/07/2013 08:07 BST | Updated 07/09/2013 06:12 BST

Some Good News - World Population Day


11 July is UN World Population Day. An easy way to remember the date is that in June this year the UN demographers upped their estimate of future global population to peak at around 11billion in about a century's time. By the dawn of the 22nd Century there will be 50% more of us, they think, give or take a few billion either way. The default reaction has been to predict doom.

Two years ago the same thing happened. Again world population day was coming up, again the UN demographers upped their estimates, but then from population peaking at nine billion before 2100 to it, instead, reaching 10billion shortly after this century's end. What's going on? Why do the official estimates keep rising? Will they rise again?

A decade ago there was a little more certainly, in fact estimates were published in 2003 that extended as far forward as the year 2300. Three centuries' worth of population change was speculated on internationally. Back then it looked as if global population levels were set to more quickly stabilize. Within the lifetimes of most people on the planet the global human population would begin to decline. Two things have changed since then. One is very good news, the second could have been anticipated.

First the good news: we are living longer. In recent years human beings have experienced what may turn out to be the fastest decline in infant mortality that has ever occurred. Despite there being far more parents today than ever before, there are far fewer grieving parents than there were in 1970. Our population levels are rising mainly because at any one time they will be more of us around to count. The same people, not new people, not extra people, but people living longer.

Second: what could have been anticipated? There has not been quite as fast a decline in global fertility as was expected in 2003. The main reason that I wrote Population 10 Billion, the book this article is based on, was to point out that UN estimates appeared not to include any adjustments for the worldwide baby boom currently under-way, an echo of early baby booms and a temporary phenomena but one, if not accounted for, which pushes up future population estimates.

The global baby boom is not a sign of rising fertility. It is simply more babies being born now because more potential mothers and fathers were born a generation ago. The overall trend is for us to quickly approach population stability. Those recent improvements in health should be expected to accelerate that slowdown. Furthermore, past global economic crises have resulted in faster than expected fertility declines, and we are in a global economic crisis again now.

There is a link between the current global population slowdown, where the rate of population-growth is rapidly falling, and the economic crisis. From 1850 until 1970 human population did not just grow worldwide, but on average grew faster each year than the year before. That, and the economic growth it both required and produced, was not sustainable.

Rising population produces economic growth because there are always greater numbers of new customers to sell to. It is easy to make rising profits when your potential market breeds quickly. But human fertility growth peaked in 1971. By 1990 we had hit "peak baby" globally. Fewer babies have been born in any year since then. Recently we hit peak-18 year old.

There are currently more young adults in the world than there have ever been; more, given current trends, than there will ever be. The number of new, often impatient to purchase, consumers is set to fall worldwide, rapidly. The rising world population is mainly a rise in older, hopefully less gullible adults. And the one prediction that none of the recent UN revisions has altered is that world population is set to soon peak, not rise forever.

Danny Dorling's, new Book - "Population 10 Billion: the coming demographic crisis and how to survive It, was published by Constable in June 2013.