Hardin's article marked the mainstream acceptance of the term "commons" as used to connote a shared resource. As Frank van Laerhoven and Elinor Ostrom have stated: "Prior to the publication of Hardin’s article on the tragedy of the commons (1968), titles containing the words 'the commons', 'common pool resources,' or 'common property' were very rare in the academic literature." They go on to say: "In 2002, Barrett and Mabry conducted a major survey of biologists to determine which publications in the twentieth century had become classic books or benchmark publications in biology. They report that Hardin’s 1968 article was the one having the greatest career impact on biologists and is the most frequently cited". System archetype In systems theory, the commons problem is one of the ten most common system archetypes. The Tragedy of the Commons archetype can be illustrated using a causal loop diagram. Application Metaphoric meaning Like Lloyd and Thomas Malthus before him, Hardin was primarily interested in the problem of human population growth. But in his essay, he also focused on the use of larger (though finite) resources such as the Earth's atmosphere and oceans, as well as pointing out the "negative commons" of pollution (i.e., instead of dealing with the deliberate privatization of a positive resource, a "negative commons" deals with the deliberate commonization of a negative cost, pollution). As a metaphor, the tragedy of the commons should not be taken too literally. The "tragedy" is not in the word's conventional or theatric sense, nor a condemnation of the processes that lead to it. Similarly, Hardin's use of "commons" has frequently been misunderstood, leading him to later remark that he should have titled his work "The Tragedy of the Unregulated Commons". The metaphor illustrates the argument that free access and unrestricted demand for a finite resource ultimately reduces the resource through over-exploitation, temporarily or permanently. This occurs because the benefits of exploitation accrue to individuals or groups, each of whom is motivated to maximize use of the resource to the point in which they become reliant on it, while the costs of the exploitation are borne by all those to whom the resource is available (which may be a wider class of individuals than those who are exploiting it). This, in turn, causes demand for the resource to increase, which causes the problem to snowball until the resource collapses (even if it retains a capacity to