Others argue that, while the combination of increasing fertility and decreasing mortality is a very real phenomenon, there is no reason to assume that this is harmful to developing countries. In The Ultimate Resource, economist Julian Simon argued that human ingenuity is a resource more important to economic growth than natural resources. Because population growth is accompanied by improvements in resource efficiency, new discoveries of natural resources, the development of substitutes, and changing consumer desires, a growing population will frequently support economic growth rather than hamper it.