What is The Gittens Index?

The Gittens Index is a mental model used for better thinking and decision-making.

How do you apply The Gittens Index?

To apply The Gittens Index, identify situations where this framework is relevant, then use it as a lens to evaluate your options and decisions. The model is most useful when combined with other complementary mental models.

What category does The Gittens Index fall under?

The Gittens Index falls under the Computer Science & Algorithms category of mental models. Other models in this category can be found on the Computer Science & Algorithms hub page.

Why is The Gittens Index important?

The Gittens Index is important because it provides a structured way to think about problems that would otherwise be approached with intuition alone. Understanding this model helps you avoid common reasoning errors and make better decisions.

Where does The Gittens Index come from?

The Gittens Index is discussed in the tradition of John Gittins.

Computer Science & Algorithms

The Gittens Index

Model #0675Category: Computer Science & AlgorithmsSource: John GittinsDepth to apply:

4 min read

Contents

1. Core Idea
2. How to See It
3. How to Use It
4. Founders & Leaders
5. Connected Models
6. One Key Quote
7. Summary & Further Reading

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Computer Science & Algorithms

Section 1

Core Idea

The Gittins index assigns a single number to each arm in a multi-armed bandit problem (with geometric discounting): it's the value of playing that arm optimally versus a fixed outside option. Choosing the arm with the highest index is optimal under the right formulation. Unlike UCB, the Gittins index is derived from the full dynamic programme; it accounts for the entire future stream of rewards and the cost of exploration. Computationally heavier than UCB, but it gives a principled, optimal policy for the discounted infinite-horizon bandit. Sub-entry under explore–exploit: when you need a rigorous rule for which option to try next, Gittins is the gold standard for the bandit setting.