For purpose of parsimony, the theory assumes that the critical drivers of social activity—in all contexts and at all levels of development—can be traced to three "interactive" master variables—population, resources, and technology. "Population" involves changes in the size, distribution, and composition of people. Each of these variables can be differentiated along a number of sub-factors or variables—depending on the issues at hand or the interest of the analyst. The same can be said about resources and technology. "Technology" refers to all applications of knowledge and skills in mechanical (equipment, machinery, etc.) as well as organizational (institutional) terms. This concept of technology encompasses both soft and hard dimensions, and often the former is as important as the latter. "Resources" are conventionally defined as that which has value to include all elements critical to human existence (such as water, air, etc.), provides a perspective on the concept of resources intimately connected to requisites for basic survival.