Factors in population growth and decline

[GliderGuider]

In another thread, I posed the question "If fossil fuel use caused global population to grow, could declining fossil fuels trigger a population drop?"

The discussion that followed got me curious about what general factors can be identified in rising and falling national populations today. I decided to dig into the numbers, so I assembled a data set for 150 countries with populations over 1 million. The data included population and per-capita GDP in constant dollars from Dr. Angus Maddison, and migration, fertility rate and life expectancy data from the CIA Worldbook. I looked at the period from 1989 to 2009.

I sliced and diced the data in a few ways. I looked at: population changes over the last 5, 10 and 20 years; changes in growth rates over the last 20 years; changes in per-capita GDP over the last 20 years; current net migration rates, fertility rates and life expectancy.

Here's what I found:

High population growth rates, whether over the last 5, 10 or 20 years are seen mainly in Africa, the Middle East and Southeast Asia. High-growth countries are characterized by rural, non-industrialized societies, high fertility rates and lower (though not very low) life expectancy. One additional wrinkle is that high 5-year growth rates are also seen in countries recovering from wars: eg. Afghanistan, Kuwait, Rwanda and iraq.

On the other hand, 20-year population decline rates are seen almost entirely in Eastern Europe, which also shows high 5 year and 10-year decline rates as well. These are industrial countries that have experienced massive amounts of social and economic destabilization since the collapse of the Soviet Union. The exhibit very low fertility rates but high life expectancy (except that Russia itself has lost over 20 years of life expectancy since the end of their empire). They also show high levels of out-migration.

10-year decline rates are also seen in a couple of central European countries (Poland and Slovenia) that exhibit the same symptoms as their Eastern European neighbors, and a couple of African countries (Lesotho and Zimbabwe) that are also characterized by social and economic destabilization, but have high fertility and low life expectancy.

5-year decline rates are seen in all the above countries, with the addition of Japan, Germany, Morocco, Sierra Leone and El Salvador.

Of the 150 countries in this study, 23 show rising population growth rates over the last 20 years. These seem to be the result of their recovery from either wars (e.g. Rwanda, Bosnia, Somalia, Iraq) or economic destabilization (Armenia, Bulgaria, Kazakhstan, the Baltic nations, Malawi, Mali, Nicaragua).

The group of 50 countries that have exhibited the steepest fall in population growth rates from 1989 to 2009 may share increasing economic instability over the period, but overall there seems little to link this behaviour in countries as diverse as Zimbabwe, Israel, Cote d'Ivoire, Egypt, Nepal, Austria , Chile, Germany Indonesia and Bangladesh.

The same can be said about the 90 or so countries "in the middle" - the group whose growth rates are declining either slowly or not at all. They are a very diverse cast of characters, with countries in obvious difficulty like Cameroon and Congo joining countries that are doing just fine, like Sweden, Canada and the USA.

Changes in population growth and decline rates do not correlate at all with changes in GDP. This implies that higher material prosperity doesn't necessarily drive growth rates down, as the Demographic Transition Model suggests. Developed nations can have high or low growth rates, as can undeveloped nations.

The same is true of life expectancy and migration rates - they show no overall correlation with changes in population growth rates.

Of all the 150 countries I reviewed, only 23 exhibited significantly rising population growth rates over the last 20 years. The other 127 had stable-to-declining rates. While this is significant, it's worth noting that the nations with stable societies, economies and politics were on the whole reducing their growth rates only very slowly, and only two - Germany and Japan - have gone into outright decline. Even their declines are modest and very recent.

The nations that are showing rapid reductions in their population growth rates and whose populations have gone into outright decline as a result are all being "helped along" by high levels of economic, social and political instability.

My conclusion from this is that population growth simply cannot be ascribed to a single theoretical factor, whether it's the demographic transition model, Virginia Abernethy's "Fertility Opportunity Hypothesis", or kristopher's theory about the division of labor. The situations in various nations are simply too diverse to permit of a single-factor explanation.

On the other hand, it's clear that instability such as economic, social or political collapse - as well as war - leads reliably to population reduction. Nothing else so far has been demonstrated to do so.

The examples of Germany and Japan are perhaps encouraging, but the effects there are quite minor, and in any event two examples out of 150 doesn't make for a reliable theoretical foundation.

If our global population is to begin to decline over the short to medium term (say the next two to five decades), then the only real force I can see that will cause it is global economic destabilization, that in turn upsets the social and political balance in large numbers of nations.

An energy descent following Peak Oil might act as a trigger for such a sand-pile avalanche of destabilization, but I don't really think it will be required. The Ponzi scheme of modern global corporate finance may be unstable enough to cause this all by itself. The burgeoning contributions of peak oil, climate change and ecological devastation simply turn that possibility into a near-certainty.

If anyone wants to see the data I used, the Excel workbook for this study is on my website here.

[provis99]

1. have you tried connecting population declines to women's rights?

It strikes me that in states with few women's rights but high income, like the Gulf States, women's rights are pretty minimal, but population growth is high, as it is in most of the Third World. Countries where women's rights are more enhanced, yet still limited, have moderate growth rates in population, such as in Latin America. Countries with the highest levels of women's rights also have the steepest declines in population growth rates.

[GliderGuider]

3. I just tried it

I used the data from the World Economic Forum's "Global Gender Gap Report 2011" that gives numerical rankings of womens' status derived across a number of social factors: health, education, political power and economic participation, for 135 countries.

I got a weak negative correlation of about -0.47 between the gender gap scores and the population decline rate over the last 20 years. The correlations of womens' rights to all other decline measures were somewhat to a lot worse.

This suggests that in most cases other factors are at least as important as womens' rights. So it's worth doing, but not to the exclusion of having a good big economic and social collapse... Wait, what?

[Gregorian]

2. Consciousness of the problem is a growing reason as well.

I know that was a reply for your other thread. But I just want to point out that rising costs of cigarettes didn't deter people as much as the realization that it kills them.

Eyes are the feedback system sensors that have still not made a conscious connection in many people. That may be due to denial. I believe it is.

Consciousness combined with personal responsibility. That's about all we can hope for.

As far as energy availability is concerned, I doubt that is going to be much of a contributing factor. Families were very large during periods of no petroleum use. Also, as I continue to work on a start-up company that will be using fuel cells for the next generation of energy conversion, the modern society will function via a different infrastructure. It may very well be even more comfortable than it is now. Energy wise only. And that doesn't even include what would be the case were fusion viable.

It's not much different than politics or habitual behavior. It just depends upon whether people are conscious of the situation, how they interpret it, and then whether they do the right thing to make for a better world. Certainly we've been going down a suicidal path. I just hope people start growing pathways between eyes and brain.

[GliderGuider]

4. The main issue is going to be the economic one, I think.

The oil supply might be a factor in the economic problems, but it's the uncomfortable economic, social and political situation that make people decide to turn of the "brat tap".

Making a decision about family size given Oil Supply X is a lot different if it's made under conditions of a low population, a growing economy and increasing social stability, than if its made under conditions of high population, a shrinking economy and disintegrating social stability. In the later case the oil supply may only be an indirect factor if it helps to trigger the socieconomic decline initially.

[Gregorian]

5. Well, it is true that people usually take a crisis to change.

I've always felt that was pathetic. And I feel that what you're saying rings true.

Then again, there is the catastrophe scenario. I see little reason for the planet sustaining things that are far out of equilibrium. There is always some kind of trigger that puts things back in line. But that's the difficult way. And one that often affects the poor and innocent first. I'm thinking Bangladesh, in the case of global warming. And disease, which I believe is the most probable way the population is going to decrease, other than personal responsibility.

[kristopher]

6. 20 years isn't going to tell you much

It is too short of a time to show whether a change in the curve is temporary or not. Take, for example, your statements on war. You note that post war periods are characterized by high growth rates, but state towards the end that war reliably reduces population. This is an indicator that the time period covered by your exercise is too short to allow long term trends to separate themselves from short term fluctuations.

You say you don't find (and I'm paraphrasing) an overarching "theoretical factor" to explain "population growth". Why would you expect to? Is that the question you were trying to answer, "is there a single theoretical factor that explains all observed variances in population density"?

Or are you looking for short term variations or population shifts?

It was my impression that you were looking for a theory that tells us what might stop us from exploding the planets population above 10B.

My recommendation is that you refine your question then design a method to look for the answer. Throwing a lot of very common data haphazardly onto a spreadsheet can be interesting but it seldom yields anything of significance on a topic as well studied as population.

But I repeat, it is fun.

[GliderGuider]

7. "Recovery" from war causes population growth

Killing people in the first place makes population decline. There's a difference.

The reason I made the statement about overarching theoretical factors is not because I expected to find one (I didn't), but because others seem to want to find one. What I want to illuminate is that the different circumstances in each country brings different factors to bear on reproductive decisions.

I do think that the breakdown of the Soviet Empire demonstrated pretty convincingly that socioeconomic collapse does wonders for population numbers. I know the timeline is too short, but on the other hand, we don't have long-term data on many declining populations in a modern industrial context. 1989 and the Soviet collapse is pretty much it (with a slight acknowlgement to Japan and Germany).

One other point - I'm not looking for factors that explain "population growth". I'm looking for factors that affect the reduction in growth to the point of outright decline. I suspect they're rather different factors. And I don't think they've been studied all that much, because people tend to be caught up looking for voluntary reduction techniques. I don't think that's a reasonable or useful quest, so I'm looking for the involuntary factors that will prove to be effective.

[kristopher]

8. Of course there is a difference between war and the recovery from war...

Is that a surprise to you? You say you want to "illuminate that the different circumstances in each country brings different factors to bear on reproductive decisions", right? Where have you done that? You point to the "breakdown of the Soviet Empire" as if that is a meaningful description of a variable. What specifically about this breakdown of an empire do you think is relevant? What specifically can it tell us about reproductive choices? Would their political break-up have had the same result if the nation wasn't one with a deeply rooted socialistic and highly specialized workforce?

You say that you're looking for something and then produce a rather meaningless piece of work that you use to (very inaccurately) dismiss the work of people who have invested huge amounts of time and study in the problem. You have not accomplished what you claimed.