A dual-axis chart displays two metrics over time with separate vertical scales. It can reveal relationships between differently scaled measures, but often makes stakeholder interpretation harder. section 7.3.2
Use this configuration cautiously:
- Prefer two separate charts when viewers might assume both metrics share units or infer correlation from similarly shaped fluctuations. section 7.3.2
- Set axis limits to make meaningful variation visible without exaggerating or hiding changes. section 7.3.2
- Label scales clearly and explain their units so stakeholders can interpret each metric independently. section 7.3.2
Graduation-rate trends
A graduation-rate series ranging from 75% to 100% may need a focused vertical axis rather than a 0%–100% scale, which can hide meaningful annual fluctuations. Pairing it with another metric on a dual axis may clarify a shared time pattern, but separate charts are often easier to read. section 7.3.2
