Prior to Malthus, population growth was seen as good for the power and wealth of a country. The rapid population growth of America was crucial in expelling England (via the Revolution) and France (via the Louisiana Purchase) from the US. But in fact, the numbers of the poor were growing in Europe in the 1700s. Malthus argued that poverty was due to an imbalance between people and resources; since population could rise very fast, it could always outstrip any gains in productivity. He did not anticipate an exponential increase in production or a voluntary decrease in fertility. However, Malthus' thinking is still important because high population levels and environmental limitations are in fact problematic today. By the eighteenth and nineteenth centuries, mortality was falling in Europe and this caused a population explosion. The productivity gains of the Industrial Revolution were nearly balanced by the increased population; per capita income of the working classes was not much improved. Fertility didn't drop until late in the nineteenth century; per capita income started to grow rapidly. The reason for the fertility decline is not well explained by declining mortality or rising standard of living or any other socioeconomic factor. The mortality and later fertility drop is called the Demographic Transition. The extension of lifespan and the freedom from continual childbearing and child rearing is one of the most important changes ever in what it means to be a human.