He developed three periods - the market period, the short period, and the long period - to understand how markets adjusted to changes in supply or demand.  
This man's early works include The Pure Theory of Foreign Trade and the article "Where to House the London Poor".  He developed three periods - the market period, the short period, and the long period - to understand how markets adjusted to changes in supply or demand.  He originated the concepts of consumer surplus and producer surplus, as well as the price-elasticity of demand.  Perhaps most famous for his theory of marginal utility, FTP, name this British economist and author of Principles of Political Economy.
This man's early works include The Pure Theory of Foreign Trade and the article "Where to House the London Poor".  
Alfred Marshall