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At the time Malthus wrote, most societies had populations at or near their agricultural limits. But by the late 20th century19th century 20th century 21st century more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901- 2000 in the sense of the Gre, the new agricultural technologies of the green revolutionThe Green revolution is a process of technological development of agricultural techniques that began in Mexico in 1944 and has since spread throughout the world. The goal of the Green revolution was to increase the efficiency of agricultural processes so had greatly expanded agricultural production throughout the world, and what famineA famine is a situation in which a certain country or area does not have enough food to feed its population. As a result, many affected by the famine are undernourished and others die of starvation. Famine was so well known in the ancient world that Famins still occurred were largely caused by warFor other uses of War, see War (disambiguation). War is conflict, between relatively large groups of people, which involves physical force inflicted by the use of weapons. Other terms for war include armed conflict hostilities and police action''. See Lim or political unrest rather than crop failure .
In addition, most technologically developed countries had by this time passed through the demographic transition, a complex social development in which total fertility rates drop drastically in response to lower infant mortality, more education of women , increased urbanization, and a wider availability of contraception. By the end of the 20th century, these countries could avoid population declines only by permitting large-scale immigration. On the assumption that the demographic transition would spread to less developed countries, the United Nations Population Division estimated that human population would peak in the late 21st century rather than continue to grow until it exhausted available resources.
Another problem is that there is no strong evidence that the human population—nor any real population—actually follows exponential growth. In plant or animal populations that are claimed to show exponential growth, closer examination invariably shows that the supposedly exponential curve is actually the lower limb of a logistic curve, or a section of a Lotka-Volterra cycle. Also, examination of records of estimated total world human population ([1] [2]) shows at best very weak evidence of exponential growth:
Clearly this is close to linear. In fact, the correlation coefficient is practically the same for linear growth, or very slow exponential growth (with a characteristic time of about 60 years).
The annual increase graph is worse; for exponential growth, it should itself be an upward trending exponential curve whereas it has actually been trending downward since 1986. Also the rate of increase should increase, whereas, of the increase between 1960 and today, five-sixths occurred in the early 1960s (presumably attributable to the Green revolution); it then rose to a peak in 1989 and has since declined to levels actually lower than 1970.
Though short-term trends, even on the scale of decades or centuries, do not necessarily disprove the underlying mechanisms promoting a Malthusian catastrophe over longer periods, the relative prosperity of the human population at the beginning of the 21st century, and the apparent failure of spectacular predictions of mass starvation or ecological collapse made by activists such as Paul Ehrlich in the 1960s and 1970s, had led many people, such as economist Julian Simon, to question its inevitability.
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