Concept

Separate percentage points from percentage change

Two extra points and twenty percent more can describe the same movement.

When it fits

A rate changes and two descriptions of the increase appear to disagree.

When to avoid it

Relative change from zero is undefined; a different description is needed for that case.

The idea

Subtract rates to obtain a percentage-point difference. Divide that difference by the original rate to obtain relative percentage change. Label the measure instead of leaving the reader to guess which denominator was used.

An example

A rate rising from 10% to 12% rises by 2 percentage points, or 20% relative to its original value.

Check your result

The stated number and its label describe the same calculation.

Keep this limit in mind

Relative change from zero is undefined; a different description is needed for that case.

Connected ideas

Evidence and sources

Supports

Relative percentage change divides the change by the original value; subtracting two percentage values instead gives a percentage-point difference.

Relative change is undefined from a zero baseline and can be difficult to interpret with negative baselines.

Prealgebra 2e, 6.2: Solve General Applications of Percent · Percent increase and decrease formula; independently derived application to percentage values

All sources (1)

Prealgebra 2e, 6.2: Solve General Applications of Percent