There are several key factors that increase the bargaining power of customers: • Customers are more concentrated than sellers • Switching costs for customers are low • Customer is well educated regarding the product • Customer is price sensitive • A large portion of a seller's sales is made up of customer purchases • The customer's own product or service is affected • There is little differentiation between products • The threat of backward integration is high. The extent to which customers can influence the market depends on their level of concentration or how well organized they are. Many small farmers produce fruit and vegetables, which they are contracted to sell to their customers, the supermarkets. The smallholder has to meet the strict quality control imposed on them by the supermarkets or risk losing the contract. This enables the supermarkets, as the customers, to exert pressure on these small suppliers. The degree to which customers are able to manipulate market forces is swayed by the how significant their purchases are in terms of the supplier's revenue. - See more at: http://www.free-management-ebooks.com/faqst/porter-06.htm#sthash.uy7MQCJd.dpuf