When the simulation starts, the youngest group on the population pyramids is highlighted. The first group of demographic statistics follows what happens to these baby girls (magenta) and their descendents (yellow) over the years.

age xx - xx : The current age of this group (or current time period, if they're all dead by now.)

girls born ~2000 : This bar shows two things. First, it says how many of this group is still alive. Second, the length of this bar represents 1000 girls born. So if the descendents bar below it is twice as long, that means that 2000 descendents of this generation have been born.

Infant mortality already took its toll on this group of girls before your aid package begins.

descendents : Children and later descendents of the generation of girls being tracked. The bar shows both how many are still alive, and the number of descendents relative to the beginning group of girls. This shows up when the girls are 15 or 20 and start having children of their own.

avg x.xx children : This statistic says, of the girls who survived to reproductive age, the average number of children they have had so far. Though mortality before reproductive age is ignored, mortality during the reproductive years is included. So lowering infant mortality has no effect on this number. But lowering adult female mortality causes it to rise.

Rate Changes

For the most part, green is good, and red is bad.

It's common for the rates here to vary a bit from what the aid type said it would do. This is partly because the aid changes rates per age group, but the statistics reported here are observed effects on the population as a whole. But there are also side effects. For example, if the birth rate is reduced, mortality may go down. No death rates were changed, but infant mortality is the highest death rate. So, if a smaller proportion of the population is infants, overall mortality falls.

+/- x.x % population fertility per woman (avg x.xx children) : The definition of fertility used is, of all women surviving to reproductive age, the average number of children expected for each. If this line is present, it's showing the %change in that fertility measure from the original population demographics. This line won't appear in the Without Aid display.

+/- x.x % population mortality (x.xx%): The definition of mortality used is deaths per capita per time step (5 years). Shows the %change in that mortality measure from the original population demographics. This line often does appear in the Without Aid display. Mortality can change just by the population becoming younger or older, without any underlying birth or death rates changing. The figure in parentheses is the current per capita mortality rate.

+/- x.x % agricultural productivity : Change in how many people can be fed in the same amount of land, basically. Educational and agricultural aid can cause this line to appear.

• Why don't these numbers match the Aid Display?

The Aid Package display says what each aid type, by itself, will do for the next step. It doesn't say what the cumulative effect of the aid will be. The With Aid folder is looking at the situation now (not projected to next step), and is comparing the statistics now to the statistics in year 2000. Thus it's reporting the cumulative effects of your aid inputs.

growth x.xx% : The overall population is growing at this rate per year.

One convenient way to look at compound interest rates like this is how long it takes to double at a particular rate. The formula for doubling time is time = ln(2) / rate. Some examples:

There are populations with negative growth rates. Italy, Japan, and Spain are several examples. In these nations today, women are having fewer than 2 children on average, and generally having them rather late in life. Immigration could make up for this less-than-replacement reproduction, but these countries don't have that much immigration, for assorted reasons.

^a Estimated population growth rate for ancient Sumer from Harvey Weiss, Yale Professor of Near Eastern Languages and Civilizations, personal communication. Modern population growth rates (1995-2000 estimates) from:

• World Resources 2000-2001 (2000) World Resources Institute, Washington, D.C., pp 296-297.

^b The high U.S. growth rate owes to immigration as well as birth rates, though its birthrate is also higher than that of its world peers.

Help Index