Math & Statistics
Percentage Change
Updated 2025-07-11
Definition
The relative difference between an old value and a new value, expressed as a percentage. The formula is ((New − Old) ÷ Old) × 100. If stock price rises from $80 to $92, the percentage change is ((92 − 80) ÷ 80) × 100 = 15%. Note that percentage change is not symmetric: a 50% increase followed by a 50% decrease leaves you at 75%, not 100%. This asymmetry explains why recovering from a 50% portfolio loss requires a 100% gain, not another 50% up.
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