IB Economics SL Internal Assessment Example

Two relevant, accurate diagrams are included and both are clearly labelled, with the market failure and the policy response shown visually.

The diagrams use correct economic relationships such as MPC, MSC, welfare loss, tax revenue, and the shift in supply caused by the levy.

The student's explanation of the diagrams is full and integrated with the article context, not just a description of labels.

A brief note clarifying whether the tax fully equals the external cost would make the policy interpretation even sharper.

The student could add one sentence on how factors such as emissions intensity or technology affect the real-world emissions reduction shown by the diagram.

Economic terminology is used appropriately and consistently throughout the commentary.

Key terms such as negative externality of production, market failure, internalisation, marginal social cost, marginal private cost, Pigouvian tax, and welfare loss are used in ways that support the argument.

The terminology is not decorative; it is used to explain the policy mechanism and its intended effects.

A slightly fuller explanation of carbon leakage would make that term more precise and show even stronger command of the concept.

More explicit signposting of a few technical labels would improve accessibility without changing the economics.