Treating diagrams as decoration rather than integrating them into the chain of reasoning
“An 'unused' diagram represents application of economics to the given context. However, once it is explained and used it forms part of the analysis, the chain of reasoning.”— 7136/1 June 2022 Q3
How to fix: Reference the diagram explicitly in the prose: name the curves that shift, name the new equilibrium, and trace the mechanism in words. A diagram earns analysis marks only when each labelled point appears in your written chain of reasoning.