world's food supply while lowering food prices. In response, the growth rate of the world's population accelerated rapidly, resulting in predictions by Paul R. Ehrlich, Simon Hopkins, and many others of an imminent Malthusian catastrophe. However, populations of most developed countries grew slowly enough to be outpaced by gains in productivity. By the early 21st century, many technologically-developed countries had passed through the demographic transition, a complex social development encompassing a drop in total fertility rates in response to various fertility factors, including lower infant mortality, increased urbanization, and a wider availability of effective birth control. On the assumption that the demographic transition is now spreading from the developed countries to less developed countries, the United Nations Population Fund estimates that human population may peak in the late 21st century rather than continue to grow until it has exhausted available resources. Recent empirical research corroborates this assumption for most of the less developed countries, with the exception of most of Sub-Saharan Africa. A 2004 study by a group of prominent economists and ecologists, including Kenneth Arrow and Paul Ehrlich suggests that the central concerns regarding sustainability have shifted from population growth to the consumption/savings ratio, due to shifts in population growth rates since the 1970s. Empirical estimates show that public policy (taxes or the establishment of more complete property rights) can promote more efficient consumption and investment that are sustainable in an ecological sense; that is, given the current (relatively low) population growth rate, the Malthusian catastrophe can be avoided by either a shift in consumer preferences or public policy that induces a similar shift. According to Malthus, population doubled every 25 years (Sandmo). Population sat at less than 17 million people in the U.S in the 1850s and a century later, according to the United States Census Bureau, population had risen to 150 million. Malthus overpopulation would lead to war, famine, and diseases and in the future, society won't be able to feed every person and eventually die. Malthus theory was incorrect, however, because by the early 1900s and mid 1900s, the rise of conventional foods brought a decline to food production and efficiency increased exponentially. More supply was being produced with less work, less resources, and less time. Processed foods had much to do with it, many wives wanting to spend less time in the kitchen and instead work. This was the beginning of technological advancements adhering to