Karl Shell is an American theoretical economist

Economist

An economist is a professional in the social science discipline of economics. The individual may also study, develop, and apply theories and concepts from economics and write about economic policy...

, specializing in macroeconomics

Macroeconomics

Macroeconomics is a branch of economics dealing with the performance, structure, behavior, and decision-making of the whole economy. This includes a national, regional, or global economy...

 and monetary economics.

Shell received an A.B.

Bachelor of Arts

A Bachelor of Arts , from the Latin artium baccalaureus, is a bachelor's degree awarded for an undergraduate course or program in either the liberal arts, the sciences, or both...

 in mathematics

Mathematics

Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...

 from Princeton University

Princeton University

Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....

 in 1960. He earned his Ph.D.

Ph.D.

A Ph.D. is a Doctor of Philosophy, an academic degree.Ph.D. may also refer to:* Ph.D. , a 1980s British group*Piled Higher and Deeper, a web comic strip*PhD: Phantasy Degree, a Korean comic series* PhD Docbook renderer, an XML renderer...

 in economics

Economics

Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

 in 1965 at Stanford University

Stanford University

The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...

, where he studied under Nobel Prize in Economics

Nobel Memorial Prize in Economic Sciences

The Nobel Memorial Prize in Economic Sciences, commonly referred to as the Nobel Prize in Economics, but officially the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel , is an award for outstanding contributions to the field of economics, generally regarded as one of the...

 winner Kenneth Arrow

Kenneth Arrow

Kenneth Joseph Arrow is an American economist and joint winner of the Nobel Memorial Prize in Economics with John Hicks in 1972. To date, he is the youngest person to have received this award, at 51....

 and Hirofumi Uzawa.

Shell is currently Robert Julius Thorne Professor of Economics

Economics

Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

 at Cornell University

Cornell University

Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...

 (succeeding notable economist and airline deregulator

Airline deregulation

Airline deregulation is the process of removing entry and price restrictions on airlines affecting, in particular, the carriers permitted to serve specific routes. In the United States, the term usually applies to the Airline Deregulation Act of 1978...

 Alfred E. Kahn

Alfred E. Kahn

Alfred Edward Kahn was an American professor, an expert in regulation and deregulation, and an important influence in the deregulation of the airline and energy industries...

 in the Thorne chair). He previously served on the economics faculty at MIT and the University of Pennsylvania

University of Pennsylvania

The University of Pennsylvania is a private, Ivy League university located in Philadelphia, Pennsylvania, United States. Penn is the fourth-oldest institution of higher education in the United States,Penn is the fourth-oldest using the founding dates claimed by each institution...

.

Shell has been editor of the Journal of Economic Theory

Journal of Economic Theory

The Journal of Economic Theory, often referred to as JET, is an important scholarly journal in the field of economics. Although the journal was originally intended as a specialty journal in mathematical economics, JET is now generally regarded as the leading journal in economic theory and one of...

, generally regarded as the leading journal in economic theory, since its inception in 1968.

Contributions to economics

While Shell has published academic articles on numerous topics in economics, he is primarily known for his contributions in three areas.

Between 1966 and 1973, Shell published three papers on inventive activity, increasing returns to scale

Returns to scale

In economics, returns to scale and economies of scale are related terms that describe what happens as the scale of production increases in the long run, when all input levels including physical capital usage are variable...

, industrial organization

Industrial organization

Industrial organization is the field of economics that builds on the theory of the firm in examining the structure of, and boundaries between, firms and markets....

, and economic growth

Economic growth

In economics, economic growth is defined as the increasing capacity of the economy to satisfy the wants of goods and services of the members of society. Economic growth is enabled by increases in productivity, which lowers the inputs for a given amount of output. Lowered costs increase demand...

. This contribution was important in its day, and later influenced the development of "new growth theory." Among others, Paul Romer

Paul Romer

Paul Michael Romer is an American economist, entrepreneur, and activist. He is currently the Henry Kaufman Visiting Professor at New York University Stern School of Business and will be joining NYU as a full time professor beginning in 2011...

 cited and heavily built upon Shell's work in his seminal papers on endogenous growth theory

Endogenous growth theory

Endogenous growth theory holds that economic growth is primarily the result of endogenous and not external force. In Endogenous growth theory investment in human capital, innovation and knowledge are significant contributors to economic growth. The theory also focus on positive externalities and...

.

Shell also made important contributions to the overlapping generations

Overlapping generations model

An overlapping generations model, abbreviated to OLG model, is a type of economic model in which agents live a finite length of time and live long enough to endure into at least one period of the next generation's lives....

 literature (and was perhaps the first to refer to the overlapping generations model by its modern name). The overlapping generations model is now a workhorse in modern macroeconomics and monetary economics.

Karl Shell is also co-inventor (with David Cass

David Cass

David Cass was a professor of economics at the University of Pennsylvania, mostly known for his contributions to general equilibrium theory. His most famous work was on the Ramsey growth model, which is also known as the Ramsey-Cass-Koopmans model.-Biography:David Cass was born in 1937 in...

) of the concept of sunspot equilibrium (and sunspots

Sunspots (economics)

In economics, the term sunspots usually refers to an extrinsic random variable, that is, a random variable that does not directly affect economic fundamentals...

).