How has population stabilization been achieved? Have those nations that have reached ZPG done so as a result of an explicit mission, in which the government and people decided that the population was increasing to rapidly?
No, for the most part, what happened was rather that these nations completed the demographic transition. (See the Population Reference Bureau's article, "Transitions in Human Population" for an excellent treatment of this phenemenon -- assigned reading, available in the Course Documents section of the Blackboard site for this class.)
The demographic transition refers to changes in demographics (population parameters) that occur during the transition from an agricultural to an industrial society. These changes lead to population stabilization.
For many of the now stable (population-wise) nations, completion of the demographic transition stabilized their population sizes without anyone consciously working towards that goal.
Specifically, the demographic transition refers to four stages that nations tend to go through as they develop. The transition is theoretical. It has actually occurred in some cases, but there are also many exceptions that we'll talk about later. The stages in the idealized transition are:
1. B and D both high and approximately equal (true early in human history)
2. B high D dropping (characteristic of some African and Mideastern nations; a result of improvements in medicine, sanitation, food supply)
3. B begins to decline, D still low (many regions of the world that we'll look at more later)
4. B and D both low, and in balance (as in many European nations)
Many developing nations are currently in stage 2. This stage is sometimes referred to as the "demographic trap" because it is a dangerous stage from the perspective of population growth. You can see why -- lowered death rates with continued high birth rates makes for rapid population growth. To achieve population stabilization, these nations must enter and complete stage 3 rapidly.
Why are so many nations apparently "stuck" in stage 2? Why is it so hard to move on to stage 3?
To go farther in the transition requires drops in both birth and death rates.
When resources are reasonably available, which do you think it is easier to do; decrease birth rates or decrease death rates?
Historically, it has been easier to decrease death rates. Advances in public health, childhood vaccines, food subsidies, and so forth all contribute to this. Basically, death is sad, and people like to prevent it!
To drop birth rates requires changes in values which must then be translated into changes in behavior. Decreasing birth rates is not simply a matter of providing access to contraceptives (although that too is important, of course!). Historically, birth rates have essentially never decreased strongly without mortality rates having decreased first.
One example of a region of the world that is in this "demographic trap" is sub-Saharan Africa. For that region, r increased by about 20% between the mid-1960's and late 1980's, despite fertility being nearly constant. This happened because life expectancy increased by approximately 25% over that time. That is, mortality decreased, without corresponding changes in fertility.
For Africa overall, r in the 1960's was approximately 2.5%, while by the late 1980's it had increased to approximately 3%, for the same reasons as described for sub-Saharan Africa. By 2011, r for Africa as a whole is down to 2.5%, partly because some African nations have made much progress in fertility declines, and also, sadly, because of the ravages of the AIDs epidemic in parts of Africa..
Important questions about how to stabilize population from the perspective of the demographic transition are:
(1) Why do nations move on into the third stage?
(2) What can be done to accelerate the movement into that stage?
Basically, what has to happen, of course, is that birth rates need to decline. It seems that, as nations move through the demographic transition (usually with an accompanying shift from an agriculturally-based economy to an industrially-based economy), birth rates begin to decline for several related reasons. These are listed briefly below, and then elaborated further.:
1. Economic development.
2. Changes in the status of women and other social changes, particularly related to increased opportunities for education and social security.
3. Decreased infant mortality
History often (but not invariably) shows that, as income and education increase, (especially of women), couples tend to have fewer children. This was, in fact, a major theme of the UN conference on population and development, held in Cairo way back in 1994. Why do these circumstances favor having fewer children?
Conversely, one could ask, "What is it about living in an agricultural society with lower income and education levels that favors having many children?" Under such circumstances, children are needed to provide extra labor on the farm and to take care of parents in their old age. Further, infant and child mortality rates are often high under such circumstances, so couples often have many children on the assumption that they won't all live to maturity. In such societies, the only acceptable role for a woman is the role of childbearer and caretaker of the home, so women have few alternatives -- and, when they are illiterate, as is true in many nations, they have little way to learn about alternatives. And, finally, there are often strong cultural or religious factors that favor having large numbers of children. For example, some religious teachings result in preference for boys. Hindus, for example, believe that only sons or grandsons may carry out funeral rites, else the soul will have to continue cycling through births and deaths. It is estimated that if this preference for boys was eliminated, India's population growth rate would decline by about 8%!
With industrialization, however, children become economic burdens instead of assets as laborers, as on the farm. This is true especially in nations that have laws against child labor.
Further, in more highly industrialized and educated societies, people tend to marry and have children later in their lives. This results in the generations becoming more widely spaced, and goes a long way towards decreasing momentum in population growth.
Industrialization and enhanced education also commonly involve improved knowledge of and access to contraceptives.
More women tend to work outside of the home -- and to be educated -- in industrialized societies as well. That is, their status often changes, such that they have recognized roles other than as childbearers. This also tends to decrease the numbers of children born per couple.
Industrialized societies often offer governmentally-supported social security programs. These provide security for people in their old age, diminishing the necessity for people to have many children to provide that security.
And, finally, improvements in medicine and sanitation often go along with industrialization and improvements in education. These improvements lower infant and child mortality rates, with the result that couples no longer feel the need to have "extra" children, in case some die. (It may seem strange that a decrease in mortality rates can decrease rates of population growth, but that seems to be how this one works!)
Historically, the transition has been completed slowly. For example, the process took centuries in the case of many of the European nations; from the time of the first begining of the industrial revolution up to the middle of this century, or something over 200 years..
(Please remember that there are many cases where the transition hasn't taken place in this orderly fashion -- this is a general model. Some exceptions are described in the following section.)
(To move to the next section in these notes (on approaches to speeding population stabilization), click the box at the bottom of the page labeled ">>." To return to the previous section, click the box labeled "<<" and to return to the master directory for the BI301 web site, click the box labeled "CONTENTS.")
This page is maintained by Patricia Muir at Oregon State University. Page last updated Oct. 25, 2012.