Alfred Marshall in the context of "Surplus (economics)"

In mainstream economics, economic surplus, also known as total welfare or total social welfare or Marshallian surplus (after Alfred Marshall), is either of two related quantities:

• Consumer surplus, or consumers' surplus, is the monetary gain obtained by consumers because they are able to purchase a product for a price that is less than the highest price that they would be willing to pay.
• Producer surplus, or producers' surplus, is the amount that producers benefit by selling at a market price that is higher than the least that they would be willing to sell for; this is roughly equal to profit (since producers are not normally willing to sell at a loss and are normally indifferent to selling at a break-even price).

The sum of consumer and producer surplus is sometimes known as social surplus or total surplus; a decrease in that total from inefficiencies is called deadweight loss.

In economics, an externality is a cost or benefit to an uninvolved third party that arises as an effect of another party's (or parties') activity. Externalities can be considered as unpriced components that are involved in either consumer or producer consumption. Air pollution from motor vehicles is one example. The cost of air pollution to society is not paid by either the producers or users of motorized transport. Water pollution from mills and factories are another example. All (water) consumers are made worse off by pollution but are not compensated by the market for this damage.

The concept of externality was first developed by Alfred Marshall in the 1890s and achieved broader attention in the works of economist Arthur Pigou in the 1920s. The prototypical example of a negative externality is environmental pollution. Pigou argued that a tax, equal to the marginal damage or marginal external cost, (later called a "Pigouvian tax") on negative externalities could be used to reduce their incidence to an efficient level. Subsequent thinkers have debated whether it is preferable to tax or to regulate negative externalities, the optimally efficient level of the Pigouvian taxation, and what factors cause or exacerbate negative externalities, such as providing investors in corporations with limited liability for harms committed by the corporation.

Lionel Charles Robbins, Baron Robbins, CH, CB, FBA (22 November 1898 – 15 May 1984) was a British economist, and prominent member of the economics department at the London School of Economics (LSE). He is known for his leadership at LSE, his proposed definition of economics, and for his instrumental efforts in shifting Anglo-Saxon economics from its Marshallian direction. He is famous for the quote, "Humans want what they can't have."

Industrial district (ID) is a place where workers and firms, specialised in a main industry and auxiliary industries, live and work. The concept was initially used by Alfred Marshall to describe some aspects of the industrial organisation of nations. At the end of the 1990s the industrial districts in developed or developing countries had gained a recognised attention in international debates on industrialisation and policies of regional development.