Absence Rate Velocity Formula
Learn how to calculate the average monthly change in an absence rate between two measurement dates.
Absence rate velocity estimates the direction and average speed of movement between a starting and ending absence rate. It is useful for summarising whether absence is rising or falling over a defined period, expressed in percentage points per month.
- 100% Free
- No Sign-Up Required
- Private & Secure
- Mobile Friendly
Monthly Absence Rate Velocity
Where:
Subtract the starting absence rate from the ending absence rate, then divide the difference by the number of months. A positive result means the absence rate increased; a negative result means it decreased.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| V - Monthly absence rate velocity | The average monthly movement in the absence rate. | percentage points/month |
| E - Ending absence rate | The absence rate measured at the end of the comparison period. | percent |
| S - Starting absence rate | The absence rate measured at the start of the comparison period. | percent |
| M - Time between rates | The number of months between the starting and ending measurements. | months |
Step-by-Step Calculation
Record the starting rate
Use the absence rate at the beginning of the selected period.
S = startingAbsenceRate
Record the ending rate
Use the absence rate at the end of the same comparison period.
E = endingAbsenceRate
Calculate the total percentage-point change
This is the direct difference between the two rates. It is measured in percentage points, not percent.
absenceRateChange = E - S
Calculate the average monthly velocity
Divide the total change by the number of months to find the average movement per month.
absenceRateVelocity = absenceRateChange / M
Calculate the relative change
This shows the total change as a proportion of the starting absence rate.
relativeRateChange = (absenceRateChange / S) * 100
Example: Absence rate increases over six months
Find the total change
4.2 - 3.5
0.7 percentage points
Find the monthly velocity
0.7 / 6
0.1167 percentage points/month
Round the displayed velocity
round(0.1167, 2)
0.12 percentage points/month
Find the relative change
(0.7 / 3.5) * 100
20.0%
Final Result
The absence rate increased by 0.70 percentage points, at an average velocity of 0.12 percentage points per month. The total relative increase was 20.0%.
Assumptions
- ✓Both absence rates use the same definition of absence and the same calculation method.
- ✓The workforce coverage and scheduled-time basis are sufficiently comparable in both periods.
- ✓The reported velocity is an average across the full period, rather than a measure of each month's movement.
- ✓The starting absence rate is greater than zero when calculating relative change.
Limitations
- !Two endpoint rates cannot show whether the change was steady, seasonal, or concentrated in one month.
- !The calculation does not adjust for workforce size, staffing mix, restructures, or changes in working patterns.
- !One-off events, such as outbreaks or disruptions, can materially affect the ending rate.
- !A positive or negative velocity describes change; it does not identify the cause of that change.
Common Mistakes to Avoid
Treating a move from 3.5% to 4.2% as a 0.7% increase rather than a 0.7 percentage-point increase.
Using inconsistent absence definitions or scheduled-hours rules for the two rates.
Entering a time period in weeks while interpreting the output as percentage points per month.
Dividing the relative change by the ending rate instead of the starting rate.
Interpreting the average monthly velocity as proof that every month changed by the same amount.
Related Formulas
Frequently Asked Questions
What is the formula for absence rate velocity?
The formula is (ending absence rate minus starting absence rate) divided by the number of months between the two measurements.
What does a negative absence rate velocity mean?
It means the ending absence rate is lower than the starting rate, so the rate declined on average over the period.
Why is the result expressed in percentage points per month?
Percentage points show the direct difference between absence rates, while per month standardises that difference over the comparison period.
How is relative absence rate change calculated?
Subtract the starting rate from the ending rate, divide by the starting rate, and multiply by 100.
Can absence rate velocity be calculated over part of a month?
Yes. Use the actual number of months as a decimal, provided both rate measurements are comparable.
Ready to calculate your result?
Use the calculator to get instant results with your own inputs.