June 22, 2009
ULAANBAATAR, Mongolia. Computer spreadsheets are a wonderful teaching tool for population projections. A projection assuming constant fertility and mortality can be formulated in one column that can be “dragged” to the right to effortlessly iterate projection cycles.
I’ve just finished teaching a three day training course to mid-career professionals in the National Statistical Office of Mongolia, joined by three staff of the Statistics Department of the Ministry of Health.
Having introduced the basic ideas of projection, I gave them an initial age distribution (from the 2000 population census of Mongolia), a set of life table “big Lx” values, and a set of age-specific birth rates, and asked them to create a spreadsheet to implement one cycle of projection. They managed this fine, with a bit of help in the later stages.
The fun really began I asked them to (i) plot the initial age distribution, then, on the same plot, (ii) the first projected age distribution, then to (iii) describe the pattern of the projected distribution in relation to the initial age, and finally to (iv) explain the pattern.
At this point the students took the initiative, asking to add plots of the next several projected age distributions. After we had done so, I asked what they thought we would see if we projected out for 200 years or so. This took all of one minute to do, and another minute or two to add the projected age distribution to the plot. Explaining why the plot looked the way it did pointed the way to stable population theory.
They liked this exercise so much that they requested a photograph of the group with the plot in the background. Here it is, with their permission!