The relative decrease change. Definition:
The relative decrease change is the difference in an indicator over two periods in time, v1 - v2, relative to the value of the indicator in the earlier period, v1.
- Where:
- v1 - is called the reference value (original, initial number);
- v2 - is called the new value (the end value).
- In our case: v1 = 50, v2 = - 10.8.
The relative decrease change. Formula:
The relative decrease change =
The actual change / |v1|
(v1 - v2) / |v1| =
- Legend:
- v1 - the original number
- |v1| - the positive value of v1, |v1| >= 0. By example: |10| = 10; |-10| = 10.
- v2 - the new value
- The actual change = v1 - v2
- / - the fraction bar (division)
Why do we use |v1| in the formula instead of v1?
- Let's see what happens if we use v1 instead of |v1|:
- Choose a random negative number as the initial value: - 89.
- Choose a random positive number for the end value: 47.
Formula and calculation:
(v1 - v2) / v1 =
(- 89 - 47) / - 89 =
-136 / - 89 ≈
1.52808988764 ≈
1.53
Although the absolute difference is negative: -136, the relative decrease change is positive: 1.53. By using |v1| instead of v1, the error is corrected.
The relative percent decrease change. Detailed calculations below
By multiplying a number by the fraction 100/100,
we change only the form of the result, not the result.
- 100/100 = 100% = 100 ÷ 100 = 1.
- n × 100/100 = (n × 100)/100 = (n × 100)%, any number.
The relative percent decrease change. Formula:
The relative percent decrease change =
The relative decrease change × 100/100 =
(The relative decrease change × 100)/100 =
(The relative decrease change × 100)%
Calculate the relative percent decrease change:
(50 - (- 10.8))/|50| =
(50 + 10.8)/|50| =
60.8/50 =
60.8 ÷ 50 =
60.8 ÷ 50 × 100/100 =
(60.8 × 100 ÷ 50)/100 =
(6,080 ÷ 50)/100 =
121.6/100 =
121.6%
The relative percent decrease change
from the original, initial value 50 to the final, end value - 10.8:
= 121.6%
The absolute (actual) difference
50 + 10.8 = 60.8
By what percentage has 50 decreased?
Answer: By 121.6%
By what percentage is - 10.8 smaller than 50?
Answer: By 121.6%
The relative percent decrease change is positive,
so we really have a relative percent decrease
(the value goes down).