TFR's are critically important from the perspective of population growth, of course, and apparently small changes in TFR result in huge changes in population growth over time.
For example, assuming that mortality patterns stayed constant:
If we reached RLF
in 2050, globally, we'd be ~10.4 billion by 2100
If we reach ½ a birth above RLF by 2050, we'd be ~17.5
billion by 2100
If we reach ½ a birth below RFL by 2050, we'd be ~5.6 billion
by 2100
In the developing world overall there was about a 50% decrease in TFR between 1960 and the late 1990's. The average TFR for the developing world (including China) in the mid-1960's was about 6.1 children per woman, decreasing to between 3 and 4 children per woman during the 1970's and 1980's. Then, the decrease in TFR's stalled at about 3-4 children per woman during the 1970's and 1980's. (Current TFR for the developing world, including China, is 2.8; excluding China it is 3.2 -- This is another case where nearly every time I revise these notes, i can revise these numbers downward!)
It is widely believed that the initial rapid drop in TFR was because of increasing availability of contraceptives, meeting a previously unmet demand for being able to plan family sizes.
The percentage of couples using contraception also increased dramatically between the early 1960's and 1990, particularly in East Asia and Latin America. In the early 1960's, fewer than 15% of couples were using any contraceptive method in any of the lesser developed regions of the world (East and South Asia, Latin America, and Africa) while by 1990, 40% or more of couples were using contraceptive methods in all regions except Africa.
As of 2006, for Latin America overall, 71% of married women are using some form of contraception (63 % were using modern methods [those available from clinics such as IUD's, pills, condoms, diaphragms, and sterilization]). (You can find data on these percentages on the Population Fact Sheet that we handed out in class.)
Corresponding percentages for Asia overall were 65% and 59% (modern methods and any method at all, respectively); Oceania 72% and 63%; Europe 68% and 53%; North America 73% and 69%; and for Africa as a whole, 28% and 22%. (For sub-Saharan Africa, only ~ 20 % of married women use any means of contraception.)
Clearly, there was a large unmet demand for contraception, and when contraception became more readily available, TFR's dropped. You can see the relationship between TFR and contraceptive use in the following figure:
As you can see, as a higher and higher percentage of women use contraception, TFRs decrease (note the strong negative slope on this figure). In fact, for the 50 nations plotted here, the correlation coefficient (r) is -0.94. (Correlation coefficients measure the strength of linear relationships. A perfect straight line fit would have a correlation of 1 [for a positive correlation] or -1 [for a negative correlation], while a random scatter of points with no linear pattern would have a correlation of zero.)(This figure is modified from the Pulliam and Haddad article on your supplementary reading list.)
You could, using data from the fact sheet, plot the relationship between TFR and another variable of interest (including but not limited to contraception use) – either for randomly chosen nations, or for those within certain regions. For example, is TFR related to expected lifespan? To the infant mortality rate? If you find some interesting relationship (this is strictly optional!) you could submit it to the Blackboard Discussion Group.
It is important to realize that, even with the approximately 50% decrease in TFR's that has occurred in developing nations over recent decades, population growth will continue to be rapid. The United Nations projects that we will add another ~1.5 billion to the global population over the next 25 years and there will be further expansion beyond that. TFR's of approximately 3 still are 50% higher than replacement level, and, combined with generally decreasing mortality rates and large momentum terms in many nations, will result in continued rapid growth.
What will be necessary to resume the decrease in TFR's? It is widely agreed that at least three components are necessary to resume the decrease:
Each is described in sections which follow. (For more detail than given in these discussions, see the article by Bongaarts in yourassigned readings ["Population policy options..."].)
(To move to the next section in these notes (on unmet demand for contraception), click the box at the bottom of the page labeled ">>." To return to the previous section on age structures, click the box labeled "<<" and to return to the master directory for the BI301 hweb site, click the box labeled "CONTENTS.")
Page maintained by Patricia Muir at Oregon State University. Last updated Nov. 3, 2008.
