Joint demand, competitive demand, derived demand and joint supply — how a shock in one market travels into another.
Why did a war two thousand miles away change the price of your bread?
The economics does not change between boards — only the reference number and the exam style. This page is written to the concept, so find your own line below and read on.
| Specification | Reference | Section |
|---|---|---|
| AQA A-Level Economics 7136 | 4.1.3.6 | The interrelationship between markets |
| Edexcel A Economics 9EC0 | 1.2.7 | Theme 1 |
| Pearson Edexcel IAL Economics | WEC11 · Unit 1 | Markets in action |
Joint demand, competitive demand, derived demand and joint supply — how a shock in one market travels into another.
AQA sets this out as 4.1.3.6 — The interrelationship between markets, inside Price determination in a competitive market. Demand, supply, and the four elasticities that carry Paper 1. It is assessed on Paper 1 and Paper 3.
Topic pages on this site are not written and abandoned. Each one gets the definition and the specification framing first, then the diagram drawn properly, then how the board actually examines it, and then the five branches below — added over months rather than dumped in one go.
This page is at the first stage. If you need this topic before then, the revision platform already covers the full specification interactively, and the Intelligence Briefing carries model answers on the essays most likely to appear.
Application is worth more marks than knowledge on this specification — AO2 carries 26–29% against AO1's 20–23%. So the examples are not decoration. They are where a third of the paper lives, and the ones that earn are the ones specific enough to be checked.
Ukrainian wheat feeds into flour, bread and animal feed, so one shock arrives three times.
Oil is an input to plastics and fertiliser, which is why its price shows up in the supermarket twice.
Electric vehicle demand raised copper prices, and copper is in everything else.
Each of these becomes a full piece in its own right, in the branches below. What is here is the hook; the argument, the data and the essay application are what the pieces are for.
Every question on this specification is marked against four assessment objectives, and they are not weighted equally. Most revision treats a topic as a body of knowledge; the paper treats it as four separate skills applied to that knowledge. This topic is examined as a define and apply topic, so here is what each objective looks like on it specifically.
| Weight | What it is | What it means on the interrelationship between markets | |
|---|---|---|---|
| AO1 | 20–23% | Knowledge and understanding of terms, concepts, theories and models | This is an AO1-heavy topic and the definitions are worth learning exactly. It is also the lightest-weighted objective, so do not stop here. |
| AO2 | 26–29% | Application of that knowledge to economic contexts | Give an example specific enough to be checked. “A public good, such as street lighting” earns; “a public good” does not. |
| AO3 | 26–29% | Analysis of issues and their impact on economic agents | Show what follows from the concept — from scarcity, or immobility, or non-excludability — rather than restating it. |
| AO4 | 22–25% | Evaluation of arguments, using evidence to support a judgement | Name the boundary. Where does the concept stop applying, and which case is genuinely contested? |
Everything above is the anchor. The pieces below take it further, and each one is built to train a particular assessment objective rather than to cover the topic again. They accumulate — nothing on this page gets deleted, it gets added to.
The revision platform covers the whole specification now, and the Academy marks your written answers against the framework examiners use. The library is the free layer, not the only one.
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