Adam Smith (1723-1790), T.R. Malthus (1766-1834), David Ricardo (1772-1823), and Karl Marx (1818-1883) lived and wrote at different times and as a result, they developed different outlooks on the future living standards of the working class. When Smith published the Wealth of Nations in 1776, the Industrial Revolution in England had only just begun (1760-1880). Malthus, Ricardo and Marx lived during a period of great change - the shift from agriculture to manufacturing. Just as Smith's optimistic outlook on the future of living standards for the working class resulted from what he was seeing when he lived, so did the pessimistic outlook of the writings of Malthus, Ricardo, and Marx. Their optimism or pessimism is reflected in the focus of their writings.