What it means
A single number rarely tells you much. Revenue of $450,000 could be a triumph or a disaster depending on what it was last month, so analysts measure change to give every figure a reference point.
The reference point is usually called the base period, and it can be the previous month, the same month last year or a budget. There are two standard ways to express it.
Absolute change is the raw difference in dollars, units or any other measure, while percentage change divides that difference by the starting value so that big and small items can be compared fairly. A $10,000 rise means very different things for a business turning over $50,000 and one turning over $5,000,000.
Direction and base matter more than most people expect. A fall from $200 to $100 is a 50% decrease, but a rise from $100 back to $200 is a 100% increase, so the same $100 swing looks different depending on which end you start from.
This is why reports should always state the comparison period clearly. In day-to-day business, change shows up in variance analysis, year-on-year growth, month-on-month trends and balance sheet movements.
Cash flow statements are built almost entirely from changes, such as the change in receivables or the change in inventory, which explain why profit and cash are rarely the same number. Good analysts also ask why something changed, not just by how much.
Splitting a change in revenue into a price effect and a volume effect, for example, shows whether growth came from selling more or from charging more, and those two stories lead to very different decisions.
In practice
Real-world examples.
Example
A retail chain compares December sales of $2,400,000 with November sales of $1,800,000. The change is $600,000, or 33.3%, which the finance team uses to judge whether the seasonal staffing plan was too cautious.
Example
A logistics manager notices that fuel costs rose from $85,000 to $93,500 over a quarter. The $8,500 increase is 10% of the starting cost, so she asks for a fuel surcharge review before the next contract round.
Example
A marketing lead sees website sign-ups fall from 4,000 to 3,200 after a redesign. That is a drop of 800 sign-ups, or 20%, so the team rolls back the new form while it investigates.
Formula
Calculation
Absolute change = New value - Old value
Percentage change = (New value - Old value) / Old value x 100
Suppose a subscription software company reported monthly revenue of $450,000 in March and $540,000 in April. The absolute change is $540,000 - $450,000 = $90,000. The percentage change is $90,000 / $450,000 = 0.20, which is 20%.
To see how base choice matters, suppose revenue then drops back to $450,000 in May. The absolute change is $450,000 - $540,000 = -$90,000, and the percentage change is -$90,000 / $540,000 = -0.1667, or about -16.7%. The dollar swing is identical, yet the percentage fall is smaller than the earlier percentage rise because the starting point is larger.Case study
Seen in the real world.
Brightwater Catering is an illustrative, fictional events business that had a record month of $120,000 in revenue and celebrated with a bonus. The owner then noticed that the previous month had been $100,000, so growth was $20,000, or 20%, and felt confident about hiring two more chefs.
Her bookkeeper asked her to look at the change in costs as well. Food and labour costs had risen from $70,000 to $96,000, an increase of $26,000, or 37.1%, which meant gross profit actually fell from $30,000 to $24,000 even though revenue climbed.
The illustrative lesson was that a single favourable change can hide an unfavourable one next to it. Brightwater paused the hiring plan, renegotiated two supplier contracts and began reporting changes in revenue, cost and profit together every month.
Watch out
Common mistakes.
- Calculating percentage change against the new value instead of the old value, which understates the size of a rise and overstates the size of a fall.
- Adding or averaging percentage changes across different periods, when they should be compounded; a 10% rise followed by a 10% fall leaves you 1% below where you began.
- Quoting a change without naming the comparison period, so readers cannot tell whether it is month-on-month, year-on-year or against budget.
Questions
People also ask.
What is the difference between absolute change and percentage change?
Absolute change is the raw difference in dollars or units, while percentage change expresses that difference relative to the starting value so different-sized items can be compared.
How do you calculate change when the starting value is zero?
Percentage change is undefined because you cannot divide by zero, so analysts report the absolute change or describe the item as new.
Is a negative change always bad?
No, a fall in costs, debt or customer complaints is a favourable change, so you must judge each movement against what it measures.
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