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Buyers are in position to exert strong bargaining power in dealing with sellers when o their costs to switch to competing brands or to substitute products are relatively high. there are big differences among the features, performance and quality of rival brands, such that many buyers have a strongly preferred brand and are thus motivated to bargain hard with the seller to obtain it on favorable terms. the number of buyers is small and/or a buyer's identity adds prestige to the seller's list of customers. Othere are so many buyers that any one buyer's purchases account for a tiny fraction of total industry sales and when the products of industry members are strongly differentiated strong or rapidly growing buyer demand creates a "sellers' market" characterized by tight supplies or shortages