An Arrow-Debreu security is a financial instrument that pays off in a specific condition or state of the world occurring in the future. Named after economists Kenneth Arrow and Gérard Debreu, these securities are theoretical constructs used primarily in the realm of general equilibrium theory and financial economics.
Each Arrow-Debreu security corresponds to a particular state of the economy, representing an uncertain outcome. For example, if the economy can have various states—such as growth, recession, or stagnation—an Arrow-Debreu security will pay a predetermined amount if a specific state occurs at a given time. These securities help in understanding and modeling risk preferences, as they allow investors to hedge against uncertain future states.
In practice, Arrow-Debreu securities serve as tools for pricing and trading risk, enabling a more efficient allocation of resources in financial markets. They highlight the importance of complete markets, where all risks can be traded and hedged, contributing to more effective financial decision-making.
