Issue trees and the profit tree

Intuition

An issue tree is a family tree for a problem. You start with one big question at the top ("why are profits down?") and keep asking "what is this made of?" until each branch is small enough to actually measure. A messy problem feels infinite; a tree makes it finite, suddenly there are only six boxes to check, not a fog.

The profit tree is the single most reused tree in all of casework, because almost every business question eventually touches money.

Framework

• Start with the equation. Profit = Revenue − Costs. Revenue = Price × Quantity. Costs = Fixed + Variable. These identities are always true, so they're always MECE.
• Keep splitting until measurable. Quantity → existing customers × purchase frequency + new customers. Don't stop at "revenue is down", push to which lever.
• Branch by one logic per level (the MECE rule from the last lesson).
• Then hypothesize. A tree isn't the answer; it's the menu. Pick the branch you suspect drives the problem and test it first.

Worked Example

A gym chain's profit drops 15%. You write the profit tree out loud: "Profit is revenue minus cost. Revenue is members × monthly fee. Costs are rent and staff (fixed) plus utilities and equipment (variable). Since rent rarely jumps overnight, my hypothesis is a revenue problem, specifically member churn. Can I see the membership trend?" In thirty seconds you've gone from a vague drop to a single number you want to see.

The tree earns its keep the moment it lets you say "I'd look here first, because…". That sentence is the whole point.

Now a SaaS company with revenue down 8%. The tree changes shape but not method: "Revenue is customers × average revenue per account. Customers move through new logos minus churn; ARPA moves through plan mix and discounting. SaaS rarely loses logos overnight, so my hypothesis is quiet ARPA erosion through discounting, can I see average deal size by quarter?" A gym, a SaaS firm: different equations, identical move, split, suspect, ask for one number.

In the room

Narrate the tree as you draw it, and make every level buy you a question. Open with: "Profit is revenue minus costs, could I see how each moved year over year?" When the data lands, kill a branch out loud: "Costs are flat, so this is a revenue problem, I'll push into price versus volume." And before you descend, justify the descent: "Rent and staff costs rarely jump overnight, so my money is on the revenue side, specifically churn." Never present the full tree and then go silent; the tree is a route, not a poster. At this moment the interviewer is scoring one thing: whether each split you name actually narrows the search, or whether you're reciting an equation and waiting to be rescued.

Pitfalls

• Drawing a beautiful tree and then never using it to pick a branch.
• Stopping one level too shallow ("it's a cost problem") instead of pushing to the driver.
• Reinventing the profit identity, Revenue − Costs is given, don't debate it.