Ladies and gents, it is my happy duty to respond briefly to some of the ideas and issues raised by Ben Wattenberg’s book and Joe Chamies’s presentation today. I will make nine quick points.

First: as both Ben and Joe have mentioned (although with differing emphasis), the prospect is for a very substantial increase in absolute numbers of human beings through the foreseeable future. 

Even with the UN Population Division’s current low variant projections, the world’s anticipated population totals in 2040 would be 25 percent higher than in it was in 2000--and one would still be talking about roughly as many human beings on earth in 2100 as in the year 2000. 

Absent world-shaking cataclysm, what we’re really talking about--at least for the decades immediately ahead--is a redistribution in the proportion of human beings within our species rather than a decline in absolute numbers.

Second: both Ben and Joe have spoken of the prospect of population aging, quite correctly noting that  (again, barring only catastrophe) it is the all-but-inevitable consequence of the trends now underway. 

But is population aging a bad thing? I would submit that--compared to the alternative--it’s not at all a bad thing!  In fact, I would say it is self-evident that the lengthening of human life is a very good thing (everything else being equal). 

In richer countries, we can have some considerable confidence in the prospect of continued “healthy aging”. Whether we will see “healthy aging” in poorer countries, including China, in the decades immediately ahead is admittedly a much more debatable question.  The potentialities of “unhealthy aging” in low income countries is an issue that should attract more of our attention today, because it could end up demand much more of our attention in the future.

Third: we should never forget the main reason we have such uncertainty and controversy over future population prospects. Plainly stated, we lack a robust theory for explaining--or predicting--fertility change. Not to put to fine a point on it: but there is no reliable scientific method by which to predict the number of babies that the currently unborn will bear. 

And that leads to my fourth point. For generations demographers have tried to describe the determinants and identify the preconditions for fertility decline. Increasingly, however, we’re seeing that there aren’t many preconditions for fertility decline.

Just what are the determinants and/or preconditions of fertility decline today?

• Urbanization? China has sub-replacement fertility, yet its population is overwhelmingly rural.
• Female literacy? Tunisia is also a sub-replacement society, yet over a third of its adult women today are illiterates.
• Income levels? Think of Sri Lanka, a sub-replacement country where real per capita income is lower today than it was in Western Europe a century ago.
• Religion? Well, guess what: sub replacement fertility is no longer just a “Protestant thing”.  In fact, low-income countries with predominantly Catholic, Buddhist, and Islamic all exhibit sub replacement fertility: think of Brazil, Thailand and Iran. And if you travel to New Delhi, Calcutta, or Bombay, you’ll see sub-replacement fertility in predominantly Hindu populations as well.

I’m tempted to suggest that the best predictor of fertility decline at this stage in world history may not be income, literacy, religion, urbanization or ethnicity, but simply calendar year--i.e., the number of years since the end of World War II.  Just look at the data: the greater the number of years that have elapsed since the end of World War II, the lower fertility rates will generally be!  This may not constitute a very good theory of fertility change, but it works curiously well as a predictive instrument.

Fifth: a healthy skepticism is never bad in the social sciences.  So when skeptics regard the dramatically shift to sub-replacement that both Ben and Joe have discussed, should they dismiss the phenomenon as a sort of statistical trick or temporary historical anomaly? 

As some of you will recall, when Ben released The Birth Dearth some seventeen years ago, the impulse of many critics was to do just that. At that time, indeed, any demographers tried to “assistant professor” Ben to death with the distinction between “period fertility” and “cohort fertility”--the idea that current-year “snapshot” representations of childbearing patterns might not accurately reflect the ultimate life-course birth patterns of real human beings, especially if changes in norms about birth timing and birth age were occurring.

I think it’s time for some skepticism about that skepticism. 

Take a look at the trends in fertility in the OECD countries--was the sub-replacement fertility of the early 1980s simply an artifact of timing decisions?  On the whole, levels are even lower today--which is to say, if mothers were “simply delaying” expected births when The Birth Dearth came out, they are still delaying those very same births seventeen years later. At some point a delayed birth becomes a birth foregone, because the clock ultimately runs out on runs out on everybody. 

It is true that in the US, a “cohort effect” of delaying fertility seems to have taken place in the late 1960s and early 1970s: that’s why our “period rate” went down so quickly, and subsequently came back up.  But among more developed countries these days, the US may qualify as the demographic exception rather than the rule. 

Elsewhere--Western Europe, for example--the period rates fell below replacement two or three decades ago, and have dropped still further in the interim.  And if the so-called “second demographic transition” theory turns out to explain those new patterns, there’s no reason to expect fertility levels in those European societies to revert toward replacement in the decades ahead, much less tomorrow.

Sixth, there is the whole question of childlessness.  As has been mentioned, in the low fertility or sub replacement countries, an increasing proportion of women today are ending their reproductive careers never having born children. 

We ought to place this tendency in perspective: to date, the prevalence of childlessness in Western Europe is still distinctly lower than it was during the pre-industrial era. Back then, in Europe West of the Danube, it was utterly commonplace for 15 percent, or 20 percent, or even 25 percent of a cohort of adult women to complete their reproductive lives never having children.

Despite that high proportion of childless women, Western Europe in an earlier age had fairly high overall levels of fertility--averages of 4 to 5 births per woman per lifetime. Today, the situation is inverted.  Now we see something like a democratization of childbearing under conditions of sub-replacement fertility: almost everyone completes their life as a parent, but typically with one or at most two children. But will sub-replacement societies remain mass-parenting societies in the future?

This brings us to my seventh point: Is there a biological imperative for human beings to procreate?  There are certainly biblical injunctions to be fruitful and multiply, but is any such impetus embedded in our human code?

Many people suspect or assume this is so, but I’m not sure that the evidence indicates as much.

In the field known as socio-biology, there are people who study what they call the “evolutionary basis of social behavior”, and “the biological foundations of human nature”.  You can take that work with as many grains of salt as you wish.  It is worth noting, however, one of the more careful analyses from this field argued sever years ago that there was indeed a biological imperative for women to be drawn to nurture children--and that we could expect the majority of women to want to nurture at least one. But do the math there: by that formulation, you could be left with a total fertility rate of about half a birth per woman per lifetime.  Under those parameters, each generation might be barely a fourth as large as the one before it. Some “biological imperative”!

Eighth: we should recognize that any proposed look at the long-term future of humanity’s numbers is perforce an applied exercise in science fiction. If we extend the horizon of the future far enough, for example, we may reach the point where the definition of “human” itself is no longer obvious: the point where you have to begin to make distinctions, for example, between human beings simplicatur and a partial human beings or cyborgs. That sort of proposition forces us to imagine things that are really too difficult for us to think about today--and such a time might arrive rather sooner than many of us would dream. 

So long as we are able to assume that the future of the human population depends upon voluntary biological reproduction, however, we can talk of population replacement in a much more limited and focused way--and this is my final point. Over the foreseeable future, population replacement will be taking place--although not in the sense that demographers typically assign to the term. In the future as today, there will surely be some communities and peoples who, because of attitude and outlook, will choose to have above-replacement fertility levels. If you posit long-term global population decline, then over long term, many many generations hence, barring the manufacture of human beings, it is those groups that will replace all of the others on our planet. 

I’ll stop there. Thank you all.

Nicholas Eberstadt is the Henry Wendt Scholar at AEI.