Ape Man

Wolfgang Lutz, Vegard Skirbekk, and Maria Rita Testa have a paper out called The Low Fertility Trap Hypothesis: Forces that may lead to further postponement and fewer births in Europe. If you like to maintain the illusion that you are well informed about the serious issues facing the world, you ought to read their paper.

But I am afraid that relatively few people will read the paper. It is scholarly and some of the jargon can be a little intimidating. It is not something that most people are in the habit of reading. So to encourage the timid out there, I am going to give a little taste of what you can expect from the paper.

As most people know, there are a lot of countries that are not producing enough children to keep their population stable. Lutz & co. spell this problem out in the beginning of their paper….

Over the last three decades birth rates have been on the decline in virtually all countries of the world, and it is estimated that already more than half of the world’s population has below replacement level fertility (Wilson 2004). An increasing number of countries have birth rates that are not just somewhat below replacement fertility, but far below that level. Measured in terms of the Total Fertility Rate (TFR), currently 34 countries have fertility levels of 1.5 or less (PRB 2005).

From there the authors of the paper make the observation that demographers have historically gotten two things wrong when making projections. The first thing they got wrong is that they assumed average longevity could only increase to certain point. The second was that they assumed that fertility would drop to replacement rate and hold steady at that point.

Both of these points have been proven false. Average longevity in many countries has gone past what were assumed to be unbreakable barriers in average longevity. And fertility rates have dropped way below replacement in a lot of countries.

According to the authors of the paper, demographers have given up on the idea of a fixed limit to average longevity. Instead, they now assume that it will continue to go up at a gradual pace. But demographers still assume that the fall in fertility will reverse itself and move towards replacement rates. This causes the authors of the paper to ask…
……..

For what reasons do these projections assume such an unusual reversal in the trend? Typically in trend analysis, one would need to come up with a very strong and convincing reason to justify such a deviation from the pervasive trend of the past 50 years of cohort experience. Even more surprisingly, not even the low fertility scenarios produced by these agencies assume a continuation of the trend of the past decades. Furthermore, none of these population projections provide the users with a clear theoretical reasoning for why, in the case of fertility, the declining trend is assumed to reverse, while in the case of mortality, it is assumed to continue. When looking at the assumed drivers of mortality decline, ranging from lifestyle factors to medical progress, there are indeed good reasons to assume that likely improvements in these fields will result in further mortality declines. But the same seems to be true for the generally assumed drivers of the fertility decline of the past decades, ranging from the decline of traditional family patterns to more female education, continuing secularization and increasing uncertainty about the future resulting from rapid social change and globalization. There is no reason to assume a reversal in the trends of many of these determinants of fertility decline in the near future. But why do projections assume a reversal in the trend of the outcome, i.e., fertility?

The authors go on to argue that we ought to look at what is causing fertility to drop instead of assuming that fertility trends will reverse for no discernible reason. As a spur to further research, the authors offer up the hypothesis that low fertility is trap from which it is very hard to get out of.

This is where the paper gets interesting. The evidence that they present for their hypothesis is compelling and well argued. From a logical standpoint, it is hard to find flaws in their hypothesis. Their hypothesis’ only real problem is that empirical data is not exhaustive enough to support authoritative arguments.

Yet, I think that anyone who takes the time to read their paper will come away with a sick feeling in their stomach. Based on my own personal observations, it is hard for me to imagine that there is any data out there that would overturn their hypothesis.

But this is where my teaser ends. I don’t think I can give a summation of the paper’s arguments for why a fertility trap is likely without making those arguments appear weaker then they are.

The true force of their argument needs to be experienced first hand. You should go read the paper.

This entry was posted on Sunday, April 22nd, 2007 at 8:01 pm and is filed under Demographics, Economics, Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.