Work out percentage increases and decreases for cities, glaciers, coastlines, tourism and development data. A new question every time, with feedback on the slips examiners see most.
The rules
- Percentage change = (new − original) ÷ original × 100.
- Always divide by the original value, the one you started from. Never the new value.
- A decrease gives a negative change. If the question asks for the percentage decrease, give its size, for example 12. A change of −12% is the same as a 12% decrease.
- Multipliers: a 20% increase is × 1.2 and a 20% decrease is × 0.8.
- To find the original value, divide by the multiplier. Do not take the percentage off the new value.
- Percentage points are the simple difference between two percentages. A rise from 60% to 75% is 15 percentage points, but a 25% increase.
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