9. In 1798, Thomas Malthus’s Essay on the Principle of Population was published. In it, he wrote: “Population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetical ratio…. This implies a strong and constantly operating check on population from the difficulty of subsistence.” Malthus was saying that the growth of the population is limited by the amount of food available to eat; people will live at the subsistence level forever. Why didn’t Malthus’s description apply to the world after 1800?