The growth of populations is clearly the most serious problem faced by the human race—Al Bartlett

Loss of biodiversity and natural habitats, depletion of the aquifers, air and water pollution, our eventual inability to grow sufficient food or to generate sufficient energy are all problems cause by a large and rapidly growing human population. Not only is it the primary cause of these problems, but no solution exists to solving these problems as long as the population continues to grow.

Populations cannot grow indefinitely in a finite environment. The United States population is currently growing at a 1% annual rate, and the worldwide population is growing at a 1.3% rate per year; rates that are fairly low compared to historic levels. If the world's population continued to grow at 1.3% for approximately 800 years, there would be 1 person for every 1 square meter of the earth's surface, and if it could continue growing at this rate for approximately 2200 years, the mass of humanity would equal the mass of the earth. Clearly before this happens we will reach a zero population growth (ZPG) level if we are lucky, and if we are not lucky we will have a period of enormous decrease in the population, whether by famine, disease or some other natural or man-made catastrophe.

When giving talks about population growth Al Bartlett makes two lists, one of things in life we consider "good," and a second that we consider "bad." The common elements of the "good" list is that they increase the population and the common element of the "bad" list is that they decrease the population. Bartlett makes the point that we have the option of selecting options off the bad list or nature will eventually make the selections for us.

Art Hobson developed The Population Game: A Socially Significant Laboratory Exercise, help students explore how populations naturally evolve. While going through the activity students encounter exponentially growing populations, the possibility of a small population crashing, even when the birth rate and lifetimes are such that the population should grow, as well as population momentum, the delay in a population's response to changes in the dynamics that control he growth.

I have created a computerized version of Hobson's Population Game. The computer version has most of the features of the original version, and some features that would not be practical without the use of a computer. The program is written in Visual Basic and run in Microsoft Excel. There is also a demonstration program, Population Momentum that helps illustrate why there is a delay to populations' responses to changes in the birth and death rates. The two programs and documentation are enclosed in the file PopulationGame.zip.