ABSTRACT
Even in the eighteenth century, the concept that the human population might outgrow its resources was not novel. In the preface to his 1798 Essay on the Principle of Population, Malthus himself wrote, “It is an obvious truth, which has been taken notice of by many writers, that population must always be kept down to the level of the means of subsistence.” The population growth rate is the birth rate minus the death rate plus immigration minus emigration. Malthus warned that population growth rates that exceeded growth rates for food supplies would lead society into a Malthusian population trap, in which the subsistence level of food per capita limited the population. The mathematics of population growth are complicated by the age and gender structure of the population. A population that is disproportionately beyond childbearing age or of a single gender carries less reproductive momentum than younger, more gender-balanced populations.
