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Net margin above operating margin means the profit came from below the operating line
Claim
The check costs one subtraction and it fired twice in a single nine-name sweep.
| ticker | op margin | net margin | trailing P/E | forward P/E | what was actually happening |
|---|---|---|---|---|---|
| AMSC | 5% | 45% | 10.97 | 23.81 | Deferred-tax valuation allowance release |
| UMC | 22% | 33% | 20.23 | 23.49 | Non-operating income — FX and investment gains |
AMSC is the severe case: a 9x gap. It screens as a profitable company on 11x earnings. It is a company earning a 5% operating margin, priced at 23.8x forward earnings and 53.6x EV/EBITDA with a beta of 3.28. Every value screen keyed on trailing P/E will surface it, and every one of them is wrong.
Why it works as a screen
Below the operating line there are only four things, and none of them are the business:
- Tax — a valuation allowance release, or a one-off rate benefit ([[pitfall-tax-valuation-allowance-round-trip-breaks-eps]])
- Investment and FX gains — marks on holdings or currency translation ([[pitfall-yahoo-misclassifies-strategic-investment-gains]], [[pitfall-unrealized-equity-marks-break-headline-pe]])
- Derivative marks — warrants and converts, which can also run the other way ([[pitfall-government-warrant-derivative-inverts-gaap-eps]])
- Disposal gains — a segment or asset sale
All four are non-recurring by construction. None will be there next year, which is exactly why the forward P/E is so much higher than the trailing one in both rows above. A forward P/E materially above the trailing P/E is the confirming signal, and it is free — it says consensus has already stripped out what the screen has not.
How to apply
- Run the subtraction on every screen output before ranking. If
net margin > operating margin, the row does not qualify on its trailing multiple, full stop. - Check the forward-vs-trailing P/E direction as the second gate. Forward above trailing = consensus expects EPS to fall = the trailing number contains something that is leaving.
- Re-rank on operating income or free cash flow. These sit above the contaminated line. For AMSC, EV/EBITDA of 53.6 told the truth that a P/E of 11.0 hid.
- The inverse case is equally common and equally misleading: a large charge below the operating line makes a healthy company screen as a collapse. Same check, same fix.
- Related: [[principle-down-a-lot-is-not-cheap]] · [[pattern-buyback-manufactured-eps-screens-as-growth]] · [[pitfall-gate-cleared-by-adjective-not-arithmetic]].