My Recent Research

Papers in Preparation

I am putting the following three drafts online, as they give some idea of what I have been up to in recent times. Truth said, all three are now in need of serious rewrites, at least in terms of what I have learnt in the last twelve months or so. On the other hand, I do think in conjunction, they point in a direction which is well worthwhile exploring, and until I do get round to the rewrite they are probably a damn sight better than nothing.

Metabolic Pathways and The Demographic Dividend, Second Draft, July 2006. | Download PDF version.

Rethinking The Demographic Transition, January 2006 | Download PDF version.

Bo Malmberg's Theory Of Stages, Sanderson and Scherbov's Life Cycle Rescaling and Demographic Maturity, February 2006 | Download PDF version

My Book

I am currently writing a book with the provisional working title:

Population, the Ultimate non-Renewable Resource?
A Study of Ageing, Fertility and Global Imbalances

We are getting older.

This commonplace is both self-evident - individually we are always that little bit older, each and every day - and surprising - Niger is getting older, Mali is getting older, Somalia is getting older. This is surprising since these are, effectively, among the youngest societies on earth (Niger, median age 15.8, Mali, median age 16.35, Somalia, median age 17.59). Now everyone is aware that Japan is getting older, everyone is aware that Germany is getting older (these are currently the two oldest societies on the planet), but Niger, Mali and Somalia!

In fact, apart from 18 'demographic outliers' as identified in the 2005 United Nations Human Development Report, each and every country on the planet is getting older. Nor is this societal 'ageing' a recent phenomenon, it starts from virually the outset of what has become known as the demographic transition - a process which began in many European societies in the late 18th and early 19th centuries. This transition begins with a sudden and sustained drop in mortality, especially in infant mortality, as a result the society becomes 'suddenly young' since the child and youth cohorts rapidly become large in comparison with older age groups, and after this it is continuous ageing all the way. Global life expectancy, for example, has more than doubled over the past two hundred years, climbing from an estimated 25 years in 1800, to the present level of 65 for men and 70 for women. During this whole period maximum life expectancy has risen steadily by more than two years a decade

So if this work is about ageing, its starting point is that this ageing is not a new or recent phenomenon (the 'discovery of ageing' is of course more recent, but that is another story) or even a phenomenon which we should view with particular preoccupation. What about the end point? Well, here is the interesting part, there is no end point, as life expectancy continues to push ever onwards and upwards we will all be living longer, and to date there does not seem to be any special biological limit to this process. That is the good news.

There is some potential bad news however, and this comes with the how. As I have said, following the sharp mortality decline which characterises the onset of the modern demographic transition ageing commences, but historically it has done so at a relatively slow rate. The difficult part of the ageing process as it affects us today is that this ageing is now proceeding more rapidly, with the most recent evidence suggesting that those societies which began the transition later are ageing even more rapidly than their predecessors. Countries like China and Brazil have experienced sharp declines in their birth rates accompanied by rapid increases in life expectancy. This means that the median age rises at historically unprecedented rates, and that these societies run the risk of becoming 'old' before they become 'rich', with old here, of course, being a fairly relative term.

Ageing then is produced by a combination of two processes, increasing life expectancy and declining fertility. Global life expectancy has more than doubled over the past two centuries, climbing from an estimated 25 years in 1800, to the present level of 65 for men and 70 for women. At the same time maximum life expectancy has risen steadily by more than two years a decade (Oeppen and Vaupel, 2002).

Perhaps the most significant detail on the fertility decline front has been the arrival of what is called below replacement fertility. This has come as something of a surprise since it is now clear that as well as lifespans having no known upper limit, fertility also seems to have no natural bottom level. Once upon a time it was thought that human fertility in modern societies would have a natural tendency to stabilise around pure replacement level. This idea, however, has no strong theoretical foundation, and also seems to lack empirical justification since fertility levels have now remained consistently below the theoretical replacement level of 2.1 children per woman for at least 25 years in 20 European countries and Japan, whilst between 1995 and 2000 a further 44 countries began to 'enjoy' below-replacement fertility. Such countries now include several Caribbean islands (Barbados, Cuba, Guadeloupe, Martinique, Puerto Rico and Trinidad and Tobago) as well as a number of countries in Eastern and South-Eastern Asia (China, the Democratic People’s Republic of Korea, Hong Kong SAR, Macao SAR, the Republic of Korea and Singapore) all of which have one thing in common: they have entered the below replacement zone even though their fertility only began its substantial decline well after 1950.

In addition, a further 13 countries seem likely to start to exhibit below-replacement-level fertility in a not too distant future: in Latin America - Argentina, Brazil, Colombia and Mexico; in North Africa - Algeria, Egypt, Morocco; in Asian - Indonesia, Iran, Philippines, Turkey, Vietnam and in sub-Saharan Africa - South Africa.

Indeed the key issue which is looming in global demographics is what will actually happen to those countries which are termed by the United Nation as the intermediate-fertility ones. Before the start of their transition to low fertility started in the years after the second world war, most of the 143 countries in what we currently describe as the developing world had total fertility levels of 5 children per woman or higher. Today, only 49 countries still do. Among the rest, 73 had a total fertility between 2.1 and 5 in the years 1995-2000, and 21 already had below-replacement fertility. Those in the 2.1 to 5 range (the so-called intermediate fertility countries accounted for 43 per cent of the world population in 2000.

The ageing process is also associated with sizeable changes in the age structure of the population, changes, and these, given our existing customary boundaries between working and retirement ages, are likely to produce a significant increase in elderly dependency ratios in the very near future across all the OECD countries.

There are however solutions available to address the problems which this rapid ageing will produce. In part it will be the objective of this book to describe and explain the changes which are taking place around us, and in part the aim will be to outine some possible responses, and in so doing to explain and justify the changes we ourselves need to make if contemporary 'ageing' is to become not a threat, but a boon and a challenge.
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Ten Theses on Longevity, Fertility, Technology and Economic Growth

1/. Life expectancy and fertility are intimately interconnected. The principal interconnection derives from the simple relation that the greater the length of the average human lifespan the higher the rate of return on the initial investment in each individual child. (Kaplan et al 2003, Kaplan and Robson, 2002). The underlying decision procedure which faces each individual in making such investment decisions has two components, investment in self and investment in offspring. Up to a certain point investment in self is also investment in offspring as there are externalities in the learning and cultural transmission process, and children obviously benefit from their parents own educational investment. But beyond this investment in children is a net charge on the individual consuming significant quantities of economic, emotional and time resources. The net outcome is that longer lives mean less newborn children, as parents invest more time and energy in both themselves and in each individual child, while the length of initial parental dependency increases steadily as both lifespan and the technological level of a society increase. In many ways Robert Fogel's idea of techno-physio evolution is in considerable harmony with this thesis...| continue reading #

Birth Postponement

The process of birth postponement may be defined as a steady and continuous increase in the age at which women give birth to their first child. Some degree of birth postponement is now a widespread, and indeed near universal, phenomenon across the OECD countries, with differences between countries existing in the extent and the speed of the process. In Western, Northern, and Southern Europe, the age of first-time mothers is now in the 26 to 29 range, up from 23 to 25 years at the start of the 1970s. In a number of European countries (in particular Spain), the mean age of women at first childbirth has now even crossed the 30 year threshold. | continue reading
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