British economist Alfred Marshall(1842-1924), known as the father of Modern Orthodox Microeconomic theory (Neoclassicism). Alfred Marshall is one of the most influential people in modern economics over all, but especially to his well-known students John Maynard Keynes and Joan Robinson. He also initiated the profession, what it is to be an economist. Being was a mathematician .Marshall's most important book, Principles of Economics, published in 1890, is equally as influential and important to economics as he is. .
When modern economists, are trying to understand why the price or quantities bought and produced of a good changes, start by looking for factors that may have shifted demand and/or supply are in direct effect of Marshall's method and way of analyses. In his book, Principles of Economics, he pointed out that the price and out of good are determined by both supply and demand. He goes on to describe how the curves of supply and demand are like a pair of scissors blades intersecting at one point to form the best conditions for the market, which is the equilibrium price, where the quantity demanded equals the quantity supplied meaning everyone's happy.
Consequently, Marshall emphasized that time was an important factor in how the markets adjust to demand and supply. So, he introduced the idea of time periods (market period, short run, long run, and secular period) assuming that the condition for equilibrium is that the market be cleared meaning that demand is equal to supply. The market period is a very short period in which the producers of a product are unable to change the quantity produced in response to a change in its price and there is perfect supply inelastic. In short run, only some factors or variables can change, like the level of output, but not plant capacity also firms can neither enter or exit the market. Short run has an upward sloping supply curve meaning that higher prices cause larger quantities to be supplied and involves two components of total costs of the firm: prime costs and supplementary costs.
