Assignment 4

Zero population growth (ZPG) is of special interest to demographers and ecologists because population numbers will remain constant over time. The net reproductive rate (NRR) is a good indication of how close a population is to ZPG, because it represents the average number of daughters that a woman is expected to produce in her lifetime. ZPG is attained when NRR equals one; every woman is exactly replacing herself. (It is not necessary to consider males, from a demographic point of view, since only women bear children.) If NRR > 1, a population will increase and if NRR < 1, a population will decrease. A value of NRR = 1 corresponds to an intrinsic growth rate of zero. ZPG is investigated in the following questions as you work within DemographyLab.


1 .		Simulate each country's population growth for 300 years and look at the time series plot of the population size. Form a hypothesis about which countries are closest to ZPG (that is, NRR = 1). Compare the NRRs of the seven countries. How well did you do with your hypothesis?

2 .		Choose a country with a high population growth rate (for example, Nigeria) and modify its fertility rates until you get as close as possible to ZPG. What types of changes to fertility rates were necessary to attain ZPG? Reset fertility rates back to their default values and change female mortality rates until you get as close as possible to ZPG.

3 .		Choose a country with a high population growth rate (for example, Nigeria) and modify its fertility rates until you get as close as possible to ZPG. What types of changes to fertility rates were necessary to attain ZPG? Reset fertility rates back to their default values and change female mortality rates until you get as close as possible to ZPG.

4 .		Choose a country with a high population growth rate (for example, Nigeria) and modify its fertility rates until you get as close as possible to ZPG. What types of changes to female mortality rates were necessary to attain ZPG? Do the same changes to male mortality rates achieve ZPG? Why or why not? Given the types of changes necessary to achieve ZPG, what realistic options are open to a nation to reach ZPG?