The Trader's Arithmetic · Lesson 3 of 6
Losing Streaks Are a Promise
A run of seven straight losses feels like proof the system is broken. Usually it is proof that arithmetic works.
Here is the probability fact that ends more trading careers than any crash: even good systems produce long losing streaks, on schedule. A system that wins 50% of the time has, on any given five trades, a 1-in-32 chance of losing all five. Run 200 trades — a modest year — and a five-loss streak is not a risk, it is a near certainty; a seven-loss streak is more likely than not.
| Win rate | Streak to expect in 200 trades |
|---|---|
| 60% | 5–6 consecutive losses |
| 50% | 7–8 consecutive losses |
| 40% | 9–10 consecutive losses |
Read that table as a promise, not a warning: if you trade a 50%-win-rate system for a year, a seven-loss run is coming. It is not feedback. It is not the market "changing". It is a coin doing what coins do — and the trader who does not know the table will meet the streak and conclude, at maximum pain, that the system failed. They will abandon it (often right before it resumes paying), or worse, double their size to "win it back" — meeting the streak's deepest point with their biggest bets.
The streak table earns its keep in two decisions:
Sizing. Your risk per trade must make the promised streak survivable — financially and emotionally. At 2% risk, an 8-loss streak costs about 15% of the account: painful, recoverable. At 10% risk, the same ordinary streak costs 57% — from which recovery needs a +132% run. The streak did not change; the sizing decided whether it was weather or an extinction event.
Judgement. Decide in advance what streak length your system's win rate makes ordinary, and grant it immunity until then. Review the system on schedule and sample size — never in the middle of a promised streak, which is precisely when your judgement is worst and the evidence means least.
Our system's target win rate implies a run of four or five straight stops as ordinary weather in any given quarter. That sentence was written into our expectations before going live, so that when the streak arrives — it will — the record shows we said so, and nobody panics into "improving" rules mid-storm.