Economic Profit & Rent — Earnings Analysis

The economics, briefly

Accounting profit subtracts the money that left your bank account. Economic profit also subtracts what you gave up to be here — the implicit cost, which is the net earnings of your next-best alternative. Earn exactly your opportunity cost and economics calls you normally profitable: no reason to move, and no reason to stay either. Economic profit is what you earn above that line, and it is the only kind that answers "should I be doing this?"

The second half is about who captures a surplus when it exists. A factor in genuinely fixed supply — a fixed number of medallions, and no more — earns economic rent: payment above what is needed to keep it in use. And an asset that earns rent indefinitely is worth rent ÷ required return. That single formula is what turns a $36,000 annual lease into a million-dollar asset, and what destroys it again when entry arrives from a direction the moat never covered.

The four working lives (annual)

Accounting profit is where the case starts, not where it ends. Three questions to carry into the model. What does each person give up to do this work, measured net and at the same scale? Which costs in the cab driver's column are paid to somebody who never drives? And how much does each answer depend on days worked per month?

The medallion — rent, capitalized

One division reproduces both observed prices within about 10%. In the case, app vehicles roughly triple; fares fell, so the lease fell, and the income stream got riskier, so the required return rose. Both moves shrink the same fraction — which is why an asset lost about 70% of its value without anyone revoking a single license.

The moat is the point. The cap blocked entry into yellow cabs. It never blocked entry into rides. Rent survives exactly as long as the moat surrounds the market rather than the product. Ask whether entry was the only cause: how medallion purchases were financed may have moved the peak too.

What you'll be able to do afterwards

• Take any earnings statement from accounting profit to economic profit, charging implicit costs net-to-net and scale-matched
• Explain normal profit as a cost rather than a result
• Identify economic rent, and say what is holding it in place
• Capitalize a rent stream into an asset price, and decapitalize an observed price back into the rent it implies
• Predict what entry does to both — and recognize when a moat protects the wrong thing

How the engagement runs

Two stages, the same rhythm as the earlier cases: specify the model before it exists, have AI build it from your spec, audit what comes back — then explain what it means and recommend something.

Where this closes the arc

Three engagements, one argument told three times. In the first, nobody had power over price and the only question was how much to produce. In the second, a patent handed one firm the power to choose the price. Here the profits look real until you count what the owner gave up — and most of what is left turns out to belong to whoever holds the scarce asset.

The medallion's rent behind a moat is the seed patent in miniature: same moat → rent → entry logic, a different legal wrapper. Drawing that link properly, rather than name-dropping it, is one of the things Stage 2 is really asking for.

Where AI fits, and where it doesn't

You draft first and AI reviews; the doer–reviewer dilemma explains why. The line for this case:

One specific thing to check for here: economic profit versus normal profit is a reliable place for a model to stumble, and it stumbles confidently.