According to critics, part of the reason the U.S. health care system is so much more expensive than those of other countries is its fragmented nature. Since each of the many insurance companies has significant administrative (overhead) costs—in part because each insurance company incurs marketing costs and exerts significant effort in weeding out high-risk insureds—the system tends to be more expensive than one in which there is only a single medical insurer. Another part of the explanation is that U.S. medical care includes many more expensive treatments than found in other wealthy countries, pays higher physician salaries, and has higher drug prices.