American Scientist

To the Editors:

Brian Hayes’s May–June 2012 Computing Science column is excellent as always. “Computation and the Human Predicament” is a very good assessment of the controversial but timely issue of limits to growth. In the comparison between the standard run and the doubled-resources run, however, I would like to see a third run. If the uncertainty in the parameter resources allows so big a leap, why not halve it and test how the model behaves? If this run gave more or less the same result as the doubled-resources run, I would doubt the model’s efficacy a little more.

Héctor Osvaldo Mato
Boulogne, Argentina

Mr. Hayes responds:

The comparison that Mr. Osvaldo Mato asks about can be made with the Web version of the World3 model available at http://bit-player.org/limits/ . One element of the model’s control panel allows the initial-resources multiplier to be set to various values between 1/8 and 32. Readers are invited to try the experiment for themselves.

In general, reducing the initial stock of resources hastens the collapse of the modeled society; increasing the initial stock delays the collapse but makes it more severe when it comes.