Jose Scheinkman: Contributions to Economic Theory and Financial Markets
Jose Scheinkman is a distinguished economist whose research spans the breadth of economic theory, from the mathematical foundations of dynamic models to the behavioral drivers of financial bubbles. His work is characterized by a rigorous approach to solving complex economic problems, often bridging the gap between theoretical physics and economic application.
Key Facts
- Dynamic Models: Established conditions for the differentiability of value functions in infinite-horizon models.
- Market Competition: Provided the modern foundation for Cournot equilibrium via capacity pre-commitments.
- Social Interactions: Researched the impact of social dynamics on urban growth, crime, and trust.
- Financial Bubbles: Analyzed how overconfidence and short-selling costs contribute to speculative bubbles.
- Mathematical Finance: Developed tools for solving continuous time models of financial time series.
Foundations of Economic Theory
One of Scheinkman's most influential contributions is his 1979 collaboration with L. M. Benveniste, titled "On the Differentiability of the Value Function in Dynamic Models of Economics." This six-page paper is critical for economists because it defines the conditions under which infinite-horizon dynamic models—models that look at economic decisions over an indefinite period—can be treated using standard differentiable calculus.
In 1983, Scheinkman shifted focus toward market competition in a joint work with David Kreps. They demonstrated that quantity precommitment (where firms commit to a specific production level in advance) and Bertrand competition (where firms compete on price) can result in Cournot outcomes. This provided the canonical modern foundation for the Cournot equilibrium, explaining it as a result of capacity pre-commitments.
Interdisciplinary Research and Cyclical Variations
Drawing on the intersection of economics and physics, Scheinkman explored the theory of social interactions. Working with Edward Glaeser and others, he tested how social dynamics influence various societal metrics. This research resulted in a series of papers covering "Growth in Cities" (1992), the mechanics of crime (1996), and the methodology for "Measuring Trust" (2000).
Beyond social interactions, Scheinkman applied natural economic theory to explain cyclical variations in specific markets. His 1994 paper with Kevin Murphy and Sherwin Rosen on "Cattle Cycles" remains one of his most widely read works, illustrating how theoretical frameworks can explain the boom-and-bust cycles of the livestock industry.
Advances in Finance and Behavioral Frictions
Since joining the faculty at Princeton, Scheinkman has focused heavily on finance, pursuing two primary trajectories. First, in collaboration with Lars Hansen, he has developed sophisticated mathematical tools to solve and test continuous time models—models where variables change smoothly and constantly—of financial time series.
Second, he has investigated behavioral and agency frictions, which are the imperfections in markets caused by human psychology or conflicts of interest. A primary focus of this work is the creation of financial bubbles. In the 2003 paper "Overconfidence and Speculative Bubbles" with Wei Xiong, Scheinkman expanded on the 1978 insights of Harrison and Kreps.
The research posits that when short selling (betting that a price will fall) is costly, the most optimistic individuals effectively set the market price. This creates a scenario where disagreements between participants generate an option value to sell to a "greater fool," thereby fueling a speculative bubble.
| Year | Key Topic | Core Contribution | Co-Authors |
|---|---|---|---|
| 1979 | Dynamic Models | Differentiability of value functions | L. M. Benveniste |
| 1983 | Market Competition | Foundation of Cournot equilibrium | David Kreps |
| 1992-2000 | Social Interactions | Urban growth, crime, and trust | Edward Glaeser et al. |
| 1994 | Cyclical Variations | Analysis of "Cattle Cycles" | K. Murphy, S. Rosen |
| 2003 | Financial Bubbles | Overconfidence and short-selling costs | Wei Xiong |
Frequently Asked Questions
What is the significance of the 1979 paper with Benveniste?
It provides the necessary conditions on model primitives that allow economists to use standard differentiable treatment when working with infinite-horizon dynamic models.
How did Scheinkman redefine the Cournot equilibrium?
He and David Kreps showed that Cournot outcomes are the result of capacity pre-commitments, even within the context of Bertrand competition.
What role does overconfidence play in financial bubbles according to Scheinkman?
When short selling is expensive, overconfident individuals can drive market prices up. Disagreements among participants create a speculative environment where assets are bought in hopes of selling them to someone else at a higher price.
What are continuous time models in the context of Scheinkman's work?
These are mathematical models used to analyze financial time series where changes occur continuously rather than at discrete intervals, developed in part through his work with Lars Hansen.
Which areas of social interaction did Scheinkman study?
He focused on the implications of social interaction theory as it relates to the growth of cities, the prevalence of crime, and the measurement of trust.