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 = 100, v2 = 8.3.
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: - 12.
- Choose a random positive number for the end value: 22.
Formula and calculation:
(v1 - v2) / v1 =
(- 12 - 22) / - 12 =
-34 / - 12 ≈
2.833333333333 ≈
2.83
Although the absolute difference is negative: -34, the relative decrease change is positive: 2.83. 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:
(100 - 8.3)/|100| =
91.7/100 =
91.7 ÷ 100 =
91.7 ÷ 100 × 100/100 =
(91.7 × 100 ÷ 100)/100 =
(9,170 ÷ 100)/100 =
91.7/100 =
91.7%
The relative percent decrease change
from the original, initial value 100 to the final, end value 8.3:
= 91.7%
The absolute (actual) difference
100 - 8.3 = 91.7
By what percentage has 100 decreased?
Answer: By 91.7%
By what percentage is 8.3 smaller than 100?
Answer: By 91.7%
The relative percent decrease change is positive,
so we really have a relative percent decrease
(the value goes down).