The Profitability Case: How to Find Why Profits Fell

What is a profitability case?

A profitability case asks you to explain why a client's profit has fallen, or to find ways to raise it. It is the most common case type in consulting interviews, because almost every client engagement touches profit and because the logic tests structure, math and judgment in 25-30 minutes. Bain's official practice case FashionCo, for instance, opens with five years of declining revenue.

The backbone never changes: profit equals revenue minus costs. Revenue equals volume times price, and costs split into variable and fixed. Strong candidates stand out through the order in which they open those branches and the speed with which they put a number on each one. For the wider interview format, see our complete case interview guide.

Build the profit tree around the client's segments

Most candidates draw the generic tree first and ask about segments later. Reverse the order. Profit rarely falls evenly across a business: one customer group, product line, channel or region usually explains most of the decline, and company-wide averages hide it.

McKinsey's prep page favors tailored structures over standard frameworks, and BCG describes structuring and identifying the key factors as the core work of a case. A segment-first tree does both. Ask one clarifying question about how the client makes money, then make your first cut along the dimension that carries most of the revenue. Keep each level mutually exclusive and collectively exhaustive, as our MECE guide explains.

A workable timing plan for a 30-minute case:

1. Clarify the goal, the time frame and the business model: 2 minutes.
2. Present the segment-first tree and a first hypothesis: 3 minutes.
3. Quantify the branches with the interviewer's data: 15 minutes.
4. Generate and size solutions: 6 minutes.
5. Recommend in one minute, with the remaining time as buffer.

Which lever moves profit most?

Price usually moves profit most. In a 1992 Harvard Business Review article, McKinsey's Michael Marn and Robert Rosiello used the average economics of 2,463 companies and found that a 1% price increase at stable volume raised operating profit by 11.1%. Equal 1% improvements in the other levers produced smaller gains.

The reason is arithmetic. A price gain at stable volume carries no extra cost, so all of it reaches the bottom line, and on a thin operating margin a small revenue gain becomes a large profit gain. In an interview this gives you a defensible order of investigation: check realized price early, even when the prompt sounds like a cost problem.

The pocket price waterfall: where revenue leaks

The same article introduced the pocket price waterfall, the walk from list price to invoice price to the money the company actually keeps (the pocket price). On-invoice discounts reduce the invoice. Off-invoice items such as volume rebates, free freight, extended payment terms and marketing allowances reduce it again, and they often sit in budgets that no single manager owns. In the article's example, pocket price ended 22.7% below invoice price.

Mentioning the waterfall in a B2B profitability case shows you know where margin hides. Ask for realized price per unit after every rebate and allowance. List price can stay flat for years while pocket price falls.

Worked example: a margin drop at a European tool distributor

Prompt (fictional): Vandenberg Tools distributes professional power tools to contractors in the Netherlands and Belgium. Revenue grew 13% in two years, yet operating profit fell from €12.0M to €9.0M. The CEO wants to know why and what to do.

Hypothesis: growth came from large accounts at lower realized prices.

Issue tree:

• Operating profit fell €3.0M (from €12.0M to €9.0M)
  • Gross profit, key accounts (large contractors)
    • Volume
    • Pocket price (list price, on-invoice discount, off-invoice leakage)
    • Purchase cost per unit
  • Gross profit, trade counter (small installers buying at branches)
    • Volume
    • Price
    • Purchase cost per unit
  • Fixed costs
    • Warehousing and logistics
    • Staff
    • IT and overhead

Data from the interviewer:

Arithmetic:

• Key accounts: 60.0 x 22% = 13.2 and 75.0 x 16% = 12.0.
• Trade counter: 40.0 x 30% = 12.0 and 38.0 x 30% = 11.4.
• Operating profit: 13.2 + 12.0 - 13.2 = 12.0 in 2024, and 12.0 + 11.4 - 14.4 = 9.0 in 2026.
• Margin effect in key accounts: at the old 22% margin, 2026 revenue would have earned 75.0 x 22% = 16.5. The 6-point drop therefore cost 16.5 - 12.0 = €4.5M, partly hidden by €3.3M of extra gross profit from growth (15.0 x 22%).

Key-account margin is the main driver. The interviewer then shows the waterfall per €100 of list price:

Pocket price fell by 5.6, or 7.1% (5.6 / 78.5). Only 2.0 of that came from the visible invoice discount. Off-invoice items grew from 3.5 to 7.1, so 3.6 of the drop sits in rebates, delivery and payment terms. Purchase cost is flat, which makes this a pricing problem.

Sizing the fix: recovering half of the 5.6 drop (2.8 per €100 of list) lifts pocket price from 72.9 to 75.7, a 3.8% increase. At stable volume that adds 75.0 x 3.8% = about €2.9M, nearly all of it profit, which brings operating profit back to about €11.9M. A 5% cut in fixed costs would add only €0.7M. Our case interview math guide drills this kind of percentage work.

From diagnosis to recommendation

Lead with the answer, then the support. A strong close sounds like this: "Profit fell €3.0M mainly because key-account pocket prices dropped 7%, driven by rebates, free delivery and longer payment terms that grew as sales chased large contractors. I recommend a pocket-price floor per account, rebates tied to margin, and a charge for next-day delivery below a minimum order. Recovering half of the pocket-price drop restores about €2.9M. The main risk is losing some contractors, so I would pilot with the 20 largest accounts first."

That structure (answer, reasons, size, risk, next step) follows the Minto Pyramid Principle: the conclusion first, then the grouped support.

Five profitability prompts to practice

1. A Belgian regional bus operator's profit per route has halved since fuel and wage costs rose. Hint: split routes by type before opening costs.
2. A Dutch online pet-food retailer grows 25% a year and still loses money. Hint: compare contribution per order with acquisition cost per customer.
3. An Austrian ski-resort operator has full slopes and falling profit. Hint: look at ticket mix and discounting before costs.
4. A German hospital-laundry service lost margin after winning three large contracts. Hint: check contract pricing against cost per kilo.
5. A coffee roaster's café chain makes money while its wholesale arm loses it. Hint: build a waterfall for wholesale accounts.

Cracking the Case sets out three business-case frameworks, including profitability, and walks through three complete candidate cases with the numbers worked out.