Stage 6

The key concept

Three marks. Students underestimate this every year. Don't.

Criterion D is worth three marks: the same as your diagrams and the same as your analysis. It's not a box you tick in the introduction and forget about. It needs to run through your entire commentary like a thread. This page is specifically about getting the concept working inside your diagrams and analysis paragraphs. The introduction can wait: we'll get to that in Stage 7.

The nine concepts

Each links to the official IB Economics guide page. Use these to check what each concept means in proper economic terms, not just the dictionary definition.

Scarcity Choice Efficiency Equity Economic Well-being Sustainability Change Interdependence Intervention

Each commentary needs a different one. And crucially: look up what the concept means in economic terms in the textbook, not just the dictionary definition. "Intervention" doesn't mean someone got involved. It means a specific government action to correct a market failure.

How to get the concept into your diagrams and analysis

1

Bold it every time

Bold the concept every time it appears. Yes, every time. The examiner needs to see it. They're reading fast. Make it impossible to miss.

2

Keep it economic

Always use the concept in a strictly economic sense. "Intervention" means a government policy tool to correct market failure: not just someone stepping in. "Efficiency" means allocative or productive efficiency: not just "things working well".

3

Explain the "why" through the concept

Use the concept to explain the motivation behind what's happening in your diagram. Why did the government decide to tax sugary drinks? Because market failure meant efficiency wasn't being achieved. Link cause to concept: in the analysis paragraph, not just the intro.

4

Connect it to your conclusion

Your closing sentences should bring the concept back around. Did the policy achieve efficiency? Did the situation improve equity? Did the intervention work? End with the concept in mind.

What good concept integration looks like

Here's an example from a real commentary (see the example IA for the full thing):

"The government's decision to implement a $0.20/oz tax represents a significant intervention intended to correct the market failure of overconsumption. As shown in Graph 2, this intervention increases the firm's costs of production, causing a leftward shift of the supply curve from S to S+tax. By using this intervention to internalise the external costs of sugary drinks, the government aims to move the market from the inefficient equilibrium at Q1 toward the socially optimum quantity at Qopt."

Notice: bolded each time, used in the economic sense, explaining the why behind the diagram shift, and directly referencing the diagram labels. That's what three marks looks like.

One-and-done doesn't cut it. Introducing the concept in your first paragraph and never mentioning it again is the most common way to lose Criterion D marks. Keep it as an underlying theme throughout.
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