The One Miss: August 2019
The Market Risk Classifier's single false positive across 35 years of crisis data. On August 5, 2019, the system classified CRISIS as the US-China trade war escalated. The S&P 500 fell about 3% and VIX jumped roughly 40% in a day. But the stress never reached crisis thresholds, and the market recovered within two weeks. Here is exactly what happened.
What happened, day by day
VIX sat below 18 and the S&P 500 traded near 2,950. Then, after the close on August 1, the US announced new tariffs on Chinese imports. The classification was STABLE going into the weekend.
China let the yuan weaken past 7 per dollar and the US named China a currency manipulator. The S&P 500 fell 3.0% to 2,844 and VIX jumped from 17.61 to 24.59 in a single session. The system classified CRISIS: the environmental and market conditions met the threshold.
The selling stopped almost immediately. VIX fell back to the high teens by August 8 and the S&P 500 climbed back to 2,938. The escalation did not broaden into systemic stress.
The market chopped in a tight range (a brief dip to 2,840 on August 14) but never broke down. By August 19, ten trading days after the call, the S&P 500 was back at 2,924, above the August 5 close, and VIX was at 16.88, far below any crisis level.
Why the scorer counts this as a false positive
A CRISIS classification is scored a hit if, within the 10 business days starting from the call, VIX reaches 35, or the S&P 500 falls 3% over 5 sessions, 6% over 10, or 10% over 20. The criteria define what “the crisis was real” means: stress that reaches crisis magnitude.
In August 2019, none of those were met. VIX peaked at 24.59 on the classification day and fell from there; it never came close to 35. The S&P 500's worst close in the window was 2,840 on August 14, essentially flat against the 2,844 trigger level, nowhere near a 3% decline. The market absorbed the trade-war news and moved on. The system flagged crisis-grade risk; the market delivered an ordinary pullback. That gap is the false positive.
What this tells you about the system
The miss is an over-call, not a blind spot
The system did not stay quiet through a crisis. It called a crisis that did not escalate. For a risk classifier, an over-call costs a hedge you did not need; a blind spot costs the drawdown you did not see coming. Of the two ways to be wrong, this is the one you can afford.
The hit criteria are deliberately strict
CRISIS is scored against real crisis magnitude: VIX 35, or multi-session S&P declines of 3 to 10 percent. August 2019 was a sharp one-day scare that reversed. Counting it as a miss keeps the 92% crisis precision honest, rather than grading every elevated day as a success.
We publish the miss
The crisis record is 12 of 13, not 13 of 13. This single false positive is documented here, on the validation page, and in the footnotes of every surface where the crisis precision appears. A system that hides its misses cannot be trusted with its hits.
Every risk shape, every episode, every hit and miss, with the scoring methodology.