Hardin argued that grazing land held in common(that is,open to any user) would always be used less carefully than private grazing lan. Each rancher would be tempted to overuse common land because the benefits would accure to the individual, while the costs of reduced land quality that results from overuse would be spread among all users. But a study comparing 217 million acres of common grazing land with 433 million acres of private grazing land showed that the common land was in better condition.

Which of the following, if true and known by the ranchers, would best help explain the results of the study?