Story, first published: Science Fiction Plus, April 1953
A trading ship, hoping to pick up its cargo of valuable habu root, finds no cargo waiting. An investigation reveals that the natives have moved out of their villages and are now living off the land. The natives have worked out an ingenious way to keep from starting a war. Like Hari Seldon in Asimov's Foundation series, they can predict a crisis point statistically, and before such a point is reached, they insure peace by deliberately retreating from progress. The expedition closes the planet to all visitors until this phenomenon can be studied. Simak makes it terribly obvious that the price of progress is war, at least in human terms, and the aliens have found a way out of the vicious cycle.
Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.59-60