Sunday, October 30, 2005

The Classic Demographic Transition Model

Alright, let me give this a whirl. In my last post, I mentioned that fertility rates were declining in DCs (Developed Countries). Let's explore a bit about population growth and trends, but let's do it as concisely as possible without getting too technical or lost in statistics. Let me do it from memory, and let me construct my own version of the classic Demographic Transition Model as shown above. There must be ten thousand of these on the net, but I played about in Photoshop to make my own. I needed to elevate my path-making and path-stroking abilities in Photoshop anyway. I need to supply a bit of background before I can talk more about both rapid and negative population growth; so here is The Classic Demographic Tranisition Model.

Very simply, the graph is based on the actual experience of the DCs. In stage one, you see both high birth rates and high death rates. The difference between the two lines represents population growth. This is what it was like in DCs in the past — several hundred years ago or more. Our antecedents made lots and lots of babies. But a lot of children died young, and people didn't really live that long anyway. Therefore, natural increase (population growth) was low and slow.

They made lots of babies because they actually needed children. At that point in history, children were an economic asset and not a liability as they are now. They could be put to work young and help on the farm or earn tiny amounts of income in other ways. Children served as old age security accounts. When you were too old to fully pull your weight, you would live with your kids. This was the extended family in action.

Several hundred years ago, or more or less, depending on the country, knowledge began to increase rapidly. This led to the industrial revolution and changed the way that we lived; the great migration from rural to urban areas began and continues. However, it wasn't just the economy that changed, but it was also knowledge in general. We learned about health and sanitation and even how to produce more food. Death rates plummeted (see the blue line in phase2). Our birth rates remained high, however, because people were simply accustomed to having and needing many children. It took a generation or two for it to sink in that people didn't need to have a dozen children in order to guarantee the survival of a few. It also took a while for them to be made truly aware that children were no longer an economic benefit but an economic liability. My paternal grandfather, for example, had fifteen brothers and sisters, but he only had one child. That's an extreme example, but it illustrates the point.

People like my grandfather did figure it out, however, and in phase three, they did begin to lower their birth rates and produce fewer and fewer children. The gap between birth rates and death rates narrowed until in recent times, mostly in the last forty or fifty years, when we entered phase four that there is once again only a small gap between birth rates and death rates.

An important point in all of this is that it is somewhat natural to have large families and somewhat adaptive to have small ones, like we do in DCs now. We must also clearly realize that the Developed Nations did experience a population explosion that was significant and lasted for up to several hundred years. It must be understood that the population explosion is not something that has just begun recently and is not something that is confined to the presently Developing Countries.

There is more to say about Less Developed Countries (LDCs) and more to say about more recent demographic trends here in DCs, but, if anyone is still with me, and I don't expect you to be, this entry is quite long enough. I'll post a part two when the planets align correctly.



Judy said...

I'm still with you!

PBS said...

Yep, me too. It all makes sense. I think the planets are looking good for tomorrow :)

George Breed said...

Yes! Please keep rolling when you are ready.

Darlene said...

Fascinating! Also of note is that the under-developed countries are the ones with the highest rate of diseases and problems. Africa, in particular. AIDS, of course, and malaria, to name a couple. Just read an article on how high the death rate is from malaria--devastating, yet nobody in the DC has really tried to work on a cure. And now the world is faced with the possibility of a Bird Flu epidemic. If it ever gets a handle, just think how this will affect all of our populations!

defiant goddess said...

Ah yes, the teacher emerges. ;)

That was an excellent summary and impressive graph.

kathy said...


Bonita said...

I'm still trying to read the info on the graph. And demo's have something to do with turntables and disc-jockeys, don't they?

I'm staying until I get this figured out.

Anvilcloud said...

For simplicity there are no numbers on the graph. However, the vertical Y-axis represents birth/death rate. In stage one, it might be more than 40/1000; in stage four it would probably be well below 20/1000. The horizontal X-axis is a timeline, but since different countries take different amounts of time to go through the process, you can't put an actual number of years on it.

Dale said...

I'm with you, AC. Darlene makes a valid point about disease in under-developed countries. But still they seem to experience the problems of over-population.