Ernst Engel — German Economist born on March 26, 1821, died on December 08, 1896

Ernst Engel was a German statistician and economist, famous for the Engel curve and the Engel's law... (wikipedia)

The poorer is a family, the greater is the proportion of the total outgo which must be used for food... The proportion of the outgo used for food, other things being equal, is the best measure of the material standard of living of a population.
With rising incomes, the share of expenditures for food products declines. The resulting shift in expenditures affects demand patterns and employment structures.