What are the key determinants of the price elasticity of demand for a product? the key determinants of the price elasticity of demand for a product are: a. government regulations, control of a key resource necessary for production, network externalities, and economies of scale. b. competition from existing firms, threat from potential entrants, competition from substitutes, bargaining power of buyers, and bargaining power of sellers. c. whether a firm has market power, whether some consumers are willing to pay more for a product than other consumers, and ability to segment the market. d. availability of close substitutes, passage of time, necessities versus luxuries, definition of the market, and share of the good in the consumer's budget. your answer is correct. e. number of firms, availability of close substitutes, and ease of firm entry and exit. which determinant is the most important? necessities versus luxuries is the most important determinant.