Porter's Five Forces Framework is a tool for analyzing competition of a business. It draws from industrial organization (IO) economics to derive five forces that determine the competitive intensity and, therefore, the attractiveness (or lack of it) of an industry in terms of its profitability. An "unattractive" industry is one in which the effect of these five forces reduces overall profitability. The most unattractive industry would be one approaching "pure competition", in which available profits for all firms are driven to normal profit levels. The five-forces perspective is associated with its originator, Michael E. Porter of Harvard University. This framework was first published in Harvard Business Review in 1979. Porter refers to these forces as the microenvironment, to contrast it with the more general term macroenvironment. They consist of those forces close to a company that affect its ability to serve its customers and make a profit. A change in any of the forces normally requires a business unit to re-assess the marketplace given the overall change in industry information. The overall industry attractiveness does not imply that every firm in the industry will return the same profitability. Firms are able to apply their core competencies, business model or network to achieve a profit above the industry average. A clear example of this is the airline industry. As an industry, profitability is low because the industry's underlying structure of high fixed costs and low variable costs afford enormous latitude in the price of airline travel. Airlines tend to compete on cost, and that drives down the profitability of individual carriers as well as the industry itself because it simplifies the decision by a customer to buy or not buy a ticket. A few carriers--Richard Branson's Virgin Atlantic is one--have tried, with limited success, to use sources of differentiation in order to increase profitability. Porter's five forces include three forces from 'horizontal' competition--the threat of substitute products or services, the threat of established rivals, and the threat of new entrants--and two others from 'vertical' competition--the bargaining power of suppliers and the bargaining power of customers. Porter developed his five forces framework in reaction to the then-popular SWOT analysis, which he found both lacking in rigor and ad hoc. Porter's five-forces framework is based on the structure–conduct–performance paradigm in industrial organizational economics. Other Porter strategy tools include the value chain and generic competitive strategies.