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 = 8, v2 = 69.9.
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: - 38.
- Choose a random positive number for the end value: 90.
Formula and calculation:
(v1 - v2) / v1 =
(- 38 - 90) / - 38 =
-128 / - 38 ≈
3.368421052632 ≈
3.37
Although the absolute difference is negative: -128, the relative decrease change is positive: 3.37. 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:
(8 - 69.9)/|8| =
- 61.9/8 =
- 61.9 ÷ 8 =
- 61.9 ÷ 8 × 100/100 =
(- 61.9 × 100 ÷ 8)/100 =
(- 6,190 ÷ 8)/100 =
- 773.75/100 =
- 773.75%
The relative percent decrease change
from the original, initial value 8 to the final, end value 69.9:
= - 773.75%
The absolute (actual) difference
8 - 69.9 = - 61.9
By what percentage has 8 decreased?
Answer: By - 773.75%
By what percentage is 69.9 smaller than 8?
Answer: By - 773.75%
The relative percent decrease change is negative,
so in this case we really have a relative percent increase instead
(the value goes up).