Use case · Margin %

Why did revenue increase but margin drop?

Revenue is up — yet gross margin % is down. Here is how WaterfallBridge pinpoints exactly which products and which drivers pulled the rate down.

The question

"Our revenue grew this quarter, but gross margin % fell. Why? Which products are responsible, and is it pricing, cost, or the mix of what we sold?"

Why traditional methods struggle

Margin % doesn't add up. You can't subtract last quarter's % from this quarter's % per product and "sum" them — percentages are ratios, not additive quantities.
Revenue and margin move in opposite directions. A simple variance report shows both numbers but never explains how one rose while the other fell.
The product population changed. New products launched and old ones were discontinued, so a like-for-like comparison is impossible by hand.
Manual Excel bridges are fragile. Separating price, cost, volume and mix effects requires careful formulas that break the moment the data shape changes.

How WaterfallBridge breaks it down

Configure the bridge with a Result of Gross Margin %, where SumY = Gross Profit (numerator) and SumN = Revenue (denominator), broken down by the Key = Product. Set the prior period as baseline and the current period as comparison. WaterfallBridge then attributes the total margin % change to each product and separates the effect of added and removed products.

Example input data

Illustrative figures. Two periods, three products — one of them brand new this period.

Product	Period	Revenue (SumN)	Gross Profit (SumY)	Margin %
Product A	Baseline	100	30	30.0%
Product A	Comparison	140	35	25.0%
Product B	Baseline	80	28	35.0%
Product B	Comparison	60	24	40.0%
Product C new	Comparison	50	5	10.0%
Total	Baseline	180	58	32.2%
Total	Comparison	250	64	25.6%

Revenue rose +70 (180 → 250) while margin % fell −6.6 pp (32.2% → 25.6%).

Example output: the margin % bridge

Contribution of each product to the −6.6 pp margin change (illustrative).

Driver	Contribution to margin %	Effect
Baseline margin %	32.2%	start
Product A — price/cost compression	−1.9 pp	down
Product B — margin improved	+0.9 pp	up
Product C — added (low-margin)	−4.8 pp	down
Mix shift (A grew, B shrank)	−0.8 pp	down
Comparison margin %	25.6%	end

The conclusion

Revenue grew, but margin % fell for two clear reasons: Product C, a new but low-margin (10%) line, added 50 of revenue and dragged the blended rate down by ~4.8 pp, and Product A's margin compressed from 30% to 25% as its volume grew. Product B actually improved, partially offsetting the decline. The action is obvious: review Product C's pricing/cost and protect Product A's margin as it scales.

Without the bridge, you'd only know "revenue up, margin down." With it, you know which product, by how much, and why.

FAQ

Why did revenue increase but margin drop?

Revenue can grow while margin % falls when growth comes from lower-margin products, when new low-margin products are added to the mix, or when unit costs rise faster than prices. WaterfallBridge decomposes the margin % change by product into price, cost, volume and mix effects — plus added and removed products — so you can see exactly which products and drivers pulled the rate down.

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