This pattern of decreasing productivity despite advances in technology is driven by a complex combination of factors. These include growing requirements to obtain market approval, which have increased clinical trial costs, and an ever-increasing base of effective drugs that has shifted efforts to drugs for more complex conditions. Rising R&D costs can be both a cause and a result of higher drug prices, as the acceptance of higher prices by payers can make increasingly expensive R&D and acquisitions of R&D projects financially viable. Increasing R&D and acquisition costs can, in turn, drive up prices.