There are several key economic theories that are important to know for the Economics Optional paper. These theories provide a foundation for understanding various economic concepts and principles. Here are some of the key economic theories you should know:

1. Classical Economics:
- Developed by Adam Smith and David Ricardo in the late 18th and early 19th centuries.
- Emphasizes the role of free markets and individual self-interest in determining economic outcomes.
- Advocates for limited government intervention and believes in the efficiency of the market mechanism.

2. Keynesian Economics:
- Developed by John Maynard Keynes in the early 20th century.
- Argues that government intervention is necessary to manage aggregate demand and stabilize the economy.
- Advocates for fiscal policy measures such as government spending and taxation to stimulate or cool down the economy as needed.

3. Monetarism:
- Developed by Milton Friedman in the mid-20th century.
- Emphasizes the importance of controlling the money supply to manage inflation and stabilize the economy.
- Argues that monetary policy is more effective than fiscal policy in influencing economic outcomes.

4. Neoclassical Economics:
- Developed in the late 19th and early 20th centuries as a response to the perceived shortcomings of classical economics.
- Combines elements of classical and Keynesian economics.
- Focuses on individual behavior, supply and demand, and the efficiency of markets.

5. Game Theory:
- Developed by John von Neumann and Oskar Morgenstern in the mid-20th century.
- Analyzes decision-making in situations where the outcomes depend on the choices of multiple individuals or organizations.
- Provides insights into strategic interactions and the behavior of firms in oligopolistic markets.

6. Development Economics:
- Focuses on understanding the economic growth and development of nations.
- Examines factors such as education, healthcare, infrastructure, and institutions that contribute to economic development.
- Includes theories like Rostow's stages of economic growth, Solow-Swan model, and Lewis model of development.

7. Behavioral Economics:
- Integrates insights from psychology into economic analysis.
- Examines how individuals make decisions that are often irrational or influenced by cognitive biases.
- Challenges the assumptions of classical economics regarding rational behavior.

These are just a few of the key economic theories that are important to know for the Economics Optional paper. Understanding these theories will provide you with a strong foundation in economic analysis and help you analyze and evaluate various economic policies and issues.