A rate doubles on two cases
Fictional example: 1 success in 10 becomes 2 in 10. Rates move from 10% to 20%, +10 points and +100% relatively. Small counts remain essential context.
In-depth practical guides
Read percentages, points and relative changes
Recalculate change and state its base, unit and denominator.
Updated :
AI-generated illustration · Reports and charts on a data review desk. Illustrative scene with no real data.
Is a rise from 20% to 25% five or twenty-five percent?
It is five percentage points and a relative increase of 25%. These describe one change in different units. The fictional examples help prevent arithmetic results from becoming performance promises.
Recover the base
Record initial and final values, period, population and rate definition. A rate based on received answers differs from one based on everyone contacted.
Calculate points
Subtract initial from final for rates expressed as percentages. From 20% to 25% is +5 points, without dividing by 20. Calculate from unrounded values.
Calculate relative change
Divide the difference by the initial value and multiply by 100. From 20 to 25 gives (25−20)/20 ×100 = 25%. Relative change is undefined when the base is zero.
Write the full result
Publish both values and name points or relative change. Include counts and period. Observed improvement alone does not establish causation; inspect population and protocol changes.
Situations and decisions
Typical situations for preparing a check. They do not describe completed assignments or actual observations.
Combining rates
Fictional groups have 10% of 10 observations and 30% of 100. The combined rate is not 20%. Sum successes and denominators if groups are compatible and disjoint.
Record to retain
- Original values and units
- Numerator, denominator and population
- Formula and published rounding
- Period and interpretation limit
Official references
Related source profiles
Related protocols
Checks before reaching a conclusion
- Is the base known?
- Is the unit named?
- Is rounding applied after calculation?
- Is causation separated from change?
A verifiable statement of base, final value, change unit and counts.
Frequently asked questions
Can percentages be averaged?
Only with appropriate denominator weighting and compatible definitions. A simple average is not automatically the combined rate.
What if the base is zero?
Publish initial and final values and absolute difference. State that relative change from zero is undefined rather than reporting an infinite percentage.
TOOLS / REGISTERS
Write a record
Negative or near-zero bases can make relative changes misleading. Explain the indicator’s meaning. Arithmetic does not repair a biased population.
- Access date and time zone
- Exact URL
- Initial and final values / denominators
- Change in percentage points
- Relative change and formula
- Reference period
- Sample / population
- Limit / uncertainty
- Decision / next action
- Review owner
- Next review