Though the word plant is sometimes used interchangeably with the words business or firm, economists use the term strictly in relationship to a physical production facility, not the company itself. So rarely is a plant or factory the sole subject of economic study, but rather it is generally the business and economic decisions that take place surrounding and within the plant that are the topics of interest. On the other hand, another economist might be more interested in the economics of plants in terms of industrial structure and organization, which might include an analysis of plants in terms of pricing decisions, industrial groupings, vertical integration, and even public policy affecting those plants and their businesses. Plants also hold relevance in an economic study as the physical centers of manufacturing, the costs of which are very much intertwined with sourcing decisions and where companies choose to set up the manufacturing portion of their business. The study of the economics of global manufacturing, for example, is of constant debate in the financial and political spheres. Taking a power plant as the example, an economist might be interested in the manufacturing economics of the power plant, which is generally a matter of costing which involves both fixed and variable costs. In economics and finance, power plants are also considered long-lived assets that are capital intensive, or assets that require investments of large sums of money. As such, an economist might be interested in performing a discounted cash flow analysis of a power plant project. Or perhaps they are more interested in the return on equity of a power plant as for regulated utilities, it may be determined by a regulatory body. In short, though the plants themselves (if understood as the physical location of manufacturing and production) are not always the primary subjects of economic study, they are at the center of the real world economic concerns.