Alfred Marshall (1842-1924) was one of the most influential economists of his generation. His book, Principles of Political Economy (1890) brought together the theories of supply and demand, marginal utility and the costs of production[?] into a coherent whole. It was the dominant textbook in England for a long period.
... age or older. The median age is 41 years. For every 100 females there are 92.6 males. For every 100 females age 18 and over, there are 90.2 males.
The median income ...