With the push model, the supply chain was based on a linear trade flow that kept some members isolated from end users. “Customer needs were only part of the equation in the push model,” which meant that “the production cycle ended up serving suppliers as well as customers” (Boulton, 1999). Given new technological developments and in particular e-commerce, UPS recognized that this model would not allow it to survive in the 21st century. The customer-driven pull model involved a non-linear process, and the new supply chain “[involved] each participant scrambling to establish direct electronic connections with the paying party – the end customer” (Boulton, 1999 ). This ultimately allowed customers to have a direct voice in the supply chain, and UPS is better able to serve its customers since this transition. Some advantages of this model are a much more efficient supply chain, less inventory, faster service, lower costs and better customer response (Boulton, 1999). UPS's ability to recognize the importance of customer-centricity in its supply chain choices has enabled it to achieve unprecedented results.