An economist is an expert in the science of economics. The individual may also study, develop, and apply theories and concepts from economics and write about economic policy. Within this field there are many sub-fields, ranging from the broad philosophical theories to the focused study of minutiae within specific markets, macroeconomics analysis, microeconomics analysis or financial analysis, involving analytical methods and tools such as econometrics, statistics, economics computational models, financial economics, financial mathematics and mathematical economics. Adam Smith is among the most famous economists, an early proponent of free market economics.

In academia
Economists work in many fields including academia, government and in the private sector, where they may also "...study data and statistics in order to spot trends in economic activity, economic confidence levels, and consumer attitudes. They assess this information using advanced methods in statistical analysis, mathematics, computer programming...and "... they make recommendations about ways to improve the efficiency of a system or take advantage of trends". as they begin. .
It is more difficult to define the professional category of "economists" than to define regulated professions such as law or engineering. While a lawyer or engineer can only be a person with a law or engineering degree, respectively, who has been licenced by state or national licencing bodies, there is not a legally-required educational requirement or licence for economists. In some job settings, the possession of a Bachelor's or Master's degree in economics is considered the minimum credential for being an economist. However, in some parts of the US government, a person can be considered an economist as long as they have four or more university courses in economics. As well, a person can gain the skills required to become a professional economist in other related disciplines, such as statistics or some types of applied mathematics, such as mathematical finance or game theory.
A professional working inside of one of many fields of economics or having an academic degree in this subject is widely considered to be an economist, and any person within any of these fields can claim to be one. Economists are also employed in banking, finance, accountancy, commerce, marketing, and business administration.
Politicians often consult economists before enacting policy, and many statesmen have academic degrees in economics (see List of politicians with economics training). However, politics and economics have not always meshed well. Peter G. Klein wrote:
Economists are not traditionally popular as policy advisors. Economics teaches that resources are limited, that choices made imply opportunities forgone, that our actions can have unintended consequences. This is typically not what government officials want to hear. When they propose an import tariff to help domestic manufacturers, we economists explain that this protection will come only at the expense of domestic consumers. When they suggest a minimum-wage law to raise the incomes of low-wage workers, we show that such a law hurts the very people it purports to help by forcing them out of work. On and on it goes. As each new generation of utopian reformers promises to create a better society, through government intervention, the economist stands athwart history, yelling "Remember the opportunity cost!" [2]

Professions

By country
According to the United States Department of Labor there were 13,000 economists in the US with a median salary of roughly $72,780 with the top ten percent earning more than US$ 129,170 annually.

Famous economists
Early economists were found in the Ancient Greek world, with Aristotle (382-322 BC) expounding in his work Topics on the topic of human production and further examining the topic in Politics. In the 1700s, one of the first economic writers was Richard Cantillon (1680-1734), who wrote the treatise Essai Sur la Nature du Commerce en Général. Early founders of economic concepts included the Scottish philosopher, economist, and historian. David Hume 1711-1776) and the so-called "classical economists": English demographer and political economist Thomas Malthus (1766-1834), political economist David Ricardo (1772–1823), and the Scottish moral philosopher and political economist Adam Smith (1723-1790).
Other early developers of economic concepts include the British philosopher, political economist John Stuart Mill (1806–1873); French economist and free trade advocate Jean-Baptiste Say (1767–1832); Prussian philosopher, political economist, and revolutionary Karl Marx (1818–1883); French classical liberal theorist and political economist, Frédéric Bastiat (1801–1850); and English economist and logician William Stanley Jevons (1835-1882).
Founders of important economic concepts who were alive during the 20th century include the Austrian economist Eugen von Böhm-Bawerk (1851–1914); the founder of the Austrian School of economics, Carl Menger(1840–1921); British economist, developer of Keynesian economics, and influential founders of modern theoretical macroeconomics John Maynard Keynes(1883–1946); American economist, health campaigner, and eugenicist Irving Fisher (1867-1947); Austrian-British economist and political philosopher, and one of the most influential members of the Austrian School of economics Friedrich Hayek (1899-1992); American economist, public intellectual, and laissez-faire capitalism advocate Milton Friedman (1912–2006).