Understanding and calculating percentages is an essential skill in business market share growth rates interest rates and many ratios are expressed as a percentage This tutorial will introduce the basics of percentages but many of the other MBTN modules will provide additional practice and ID: 553262
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Slide1
Percentages
Understanding and calculating percentages is an essential skill in business – market share, growth rates, interest rates, and many ratios are expressed as a percentage. This tutorial will introduce the basics of percentages, but many of the other MBTN modules will provide additional practice and contexts.
Author: Stu James
© 2016 Stu James and Management by the Numbers, Inc.Slide2
100,000
16
8002 Million
Are these numbers significant?
Introduction
MBTN | Management by the Numbers
Introduction
2
“Baseball is 90 percent mental and the other half is physical
.”
- Yogi Berra,
Baseball Player and Coach
Without context, numbers mean very little. Percentages are one important way to provide context to a value in a single calculation. Let’s illustrate this using 4 numbers:Slide3
100,000
Votes
16 Wins800 Computers
$2 Million of RevenuesIntroduction
MBTN | Management by the Numbers
Introduction
3
The first question we might ask is: 100,000 of what? So, let’s add that and see if it helps.
It does help some because the item in question provides certain associations, but is it sufficient? Consider the following regarding 100,000 votes.
Jane received
100,000
votes for mayor of the city.
100,000
people voted for the independent presidential candidate for the country. Slide4
Introduction
MBTN | Management by the Numbers
Introduction
4
We can easily see how the context of size of voting population could have a large impact on how we view the number
100,000
.
Let’s add two important values to those statements to further enhance the meaning.
Jane received
100,000
votes for mayor of the city out of 200,000 total votes cast.100,000 people voted for the independent presidential candidate for the country out of 10 million total votes
cast.Slide5
Introduction
MBTN | Management by the Numbers
Introduction
5
By dividing the number of votes the two candidates received by the total votes cast, this gives us an idea of each candidate’s popularity relative to the voting population.
Jane won 100,000 / 200,000 votes =
.50
of votes cast.
The independent presidential candidate won 100,000 / 10,000,000 votes =
.01
This “ratio” (votes received relative to voting population) tells us that Jane is a very popular mayoral candidate (or had very weak or little competition), whereas the independent candidate for president was not particularly popular.Slide6
Calculating Percentages
MBTN | Management by the Numbers
Calculating Percentages
6
Definition
Percent (%)
= 100 * (Part / Whole
)
Or perhaps easier than multiplying by 100, is to realize that a decimal is equivalent to the percent (e.g. 20 / 100 =.20 = 20%)
Example:
There are 20 apples in total. Joe has 5 apples. Joe’s apples represent what percent of all the apples?
To convert this ratio to percentages we multipl
y
the ratio by 100 and add a percent sign (%) to the result. So ¼ = .25 becomes 25%. When working with percentages, the whole may be considered 100, and percentages part of that 100.
P
ercent is actually from the Latin “per centum”
meaning
by
the
hundred. This leads us to our definition.Slide7
Calculating Percentages
MBTN | Management by the Numbers
Calculating Percentages
7
Another common use of percentages is for calculating
growth rates
. That is, what is the percentage change (growth
rate %)
compared to a previous time period? This is really a variation on the previous definition, but since growth doesn’t really qualify as a portion, let’s use slightly different terminology.
Going back to our voting
examples, let’s calculate
what percent of total votes each candidate won: Jane won 100 * (100,000 / 200,000) = 50% of votes cast. The independent presidential candidate won 100 *(100,000 / 10,000,000) = 1%
of votes cast.
Answer:
First calculate the ratio of Joe’s Apples / Total = 5 / 20 = .25
Then multiply by 100 and add percent sign = 25%Slide8
Calculating Percent growth
MBTN | Management by the Numbers
Calculating Percent Growth
8
Definition
Percent (%) Growth
= 100 * (Change / Base), or
100 * (New – Base) / Base
Example:
I
n 2015, sales of the Carp-O-
Matic were 800K units. In 2016, sales reached 1 million units. What was the percent growth from 2015 to 2016?
Answer:
Growth % = 100 * (Change in sales from 2015 to 2016) / 2015 sales
100 * (1,000,000 – 800,000) / 800,000
100 * (200,000 / 800,000) = 100 * .25
= 25% Growth
Insight
Notice that the underlying equation for calculating the percent is really the same for both definitions, only the context is different.Slide9
Calculating Percent Growth
MBTN | Management by the Numbers
Calculating Percent Growth
9
Definition
Projected
= Base + Base * Growth % or Base * (1 + Growth %)
We can also use the percent growth rate to project future values by changing the formula around.
Example:
If Carp-O-
Matic
maintains the same growth rate (%) for the following year, what will sales be in 2017?
Answer:
Projected = Base + Base * Growth %
2016 Sales + 2016 Sales * Growth %
1,000,000 + 1,000,000 * 25%
1,000,000 + 1,000,000 * .25
1,000,000 + 250,000
= 1,250,000 UnitsSlide10
Calculating Percent Growth
MBTN | Management by the Numbers
Calculating Percent Growth
10
Now let’s return to our votes example to see how growth rates might change the significance of these values.
Example:
In the previous mayoral race, Jane received
150,000
votes for mayor of the city against the same challenger.
In the previous presidential race
,
20,000 people voted for the same independent presidential candidate.
Answer:
Jane’s growth (%) = 100 * (100,000 – 150,000) / 150,000
=
100 * -50,000 / 150,000 =
- 33.3% growth
Pres. Candidate % = 100 * (100,000 – 20,000) / 20,000 = 100 * 80,000 /
20,000 =
400% growth
Based on this information, it appears that Jane’s popularity is on the decline while the independent candidate is growing rapidly. Again, another change in perspective, which may be important to consider.Slide11
Examples
MBTN | Management by the Numbers
Examples
11
16
Wins (for an NFL team, a 16 game season vs. for a NBA team, an 82 game season).
800
Computers for a university with 1,000 students vs. a university with 16,000 students.
$2 Million
of a product’s revenues in the current year if last year’s product revenues were $200,000 and total revenues were $400 million.
Time to revisit our three remaining values from the beginning of the tutorial, but now let’s use percentages to help us appreciate the context.Question: Calculate the appropriate percentages and then explain in your own words how the percentages changed the meaning of the numeric value.Slide12
Examples
MBTN | Management by the Numbers
Examples
12
16
Wins (for an NFL team – 16 game season vs. for a NBA team – 82 game season).
Answer:
NFL Team (%)
= 100 *
(16 / 16)
=
100 *
1 =
100% winning percentage
NBA Team (%)
= 100 *
(16 / 82)
= 100 *
.195 =
19.5% winning percentage
Based on this information, we might conclude that the NFL team was likely the best in their league as they won every game (100%) and that the NBA team was probably one of the poorest in their league (they only won 19.5% of their games), even though each team had 16 wins.Slide13
Examples
MBTN | Management by the Numbers
Examples
13
800
Computers for a university with 1,000 students vs. a university with 16,000 students.
Answer:
1,000 Student U (%)
= 100 *
(800 / 1000)
=
100 *
.80 =
80%
16,000 Student U (%)
= 100 *
(800 / 16000)
= 100 *
.05 =
5%
We can tell that the 800 computers is more significant relative to the student population in the first university. However, we don’t really know what this represents. Does it mean that 80% and 5% of the students have computers? Or maybe it represents how many computers had to be purchased upon arrival on campus? Or maybe it refers to a brand of computer. We really don’t know. Without more information, we really can’t conclude too much.
Proceed with caution!Slide14
Examples
MBTN | Management by the Numbers
Examples
14
$2 Million
of a product’s revenues in the current year if last year’s product revenues were $200,000 and total revenues were $400 million.
Answer:
Growth (%)
= 100 *
(2,000,000 – 200,000) / 200,000)
=
100 *
9.0 =
900%
% of Total Revenues
= 100 *
(2,000,000 / 400,000,000)
= 100 *
.005 =
.5%
This one is particularly interesting. We can see the product’s revenues grew considerably over the previous year’s (900% or 10x last year). On the other hand, that product’s overall contribution to revenues is only .5% (that is, the product represents .5% of the company’s total revenues or sales). So certainly, due to the year over year growth, this could be an exciting new product, but right now, not very significant.Slide15
Examples
MBTN | Management by the Numbers
Examples
15
Follow-up Question
: If the product grew by the same amount next year and total revenues for the company remained constant at $400 million, what would be the product’s revenues next year and what % of total revenues would that represent?
Answer:
Next Year’s Revenues
=
2,000,000 * (1 + 900%)
= 2,000,000 * (1 + 9.00)
= 2,000,000 * 10 = 20,000,000
% of Total Revenues
= 100 *
(20,000,000 / 400,000,000)
= 100 *
.05 =
5%
By projecting next year’s revenues, we can see how quickly this product could become an important part of the company’s overall revenues. The question is, then, whether that growth rate will continue into the future!Slide16
Further Reference
16
Further Reference
MBTN | Management by the Numbers
MBTN Modules on Growth Rates, Market Share Metrics I, and
Financial Metrics I.