The market prices scenarios, not destinations: what the October 5 session teaches investors

In the first trading session after the October 4 vote, the Ibovespa rose 7.7% and closed at 206,911 points, a record closing high. The dollar fell 4.12% to R$5.00, its biggest daily drop in more than eight years. Long term interest rates dropped by more than 130 basis points. All in a single day.

What did not change between Friday and Monday is as revealing as what did. On the same day, the central bank’s Focus survey still projected 2026 inflation at 5.01%, above the 4.5% ceiling of the target range, and GDP growth of 1.85%. The short term fundamentals were the same. What changed was the expectation about what comes next. The market did not price a fact. It priced a scenario.

That matters because expectations can be confirmed or contradicted, and prices follow. An asset that jumps in one day on anticipation can give back part of the move in another, when the fact arrives different from what was expected or more slowly. Regardless of the runoff result, what the October 5 session shows does not depend on it: the distance between price and reality can be large, and that is where money gets lost.

We are wary of decisions made on the day’s headline, in either direction. Those who bought in the euphoria paid for the scenario already built into the price. Those who sold in the anxiety of the previous days realized a loss and missed the move that followed. A good decision has a horizon, has entry and exit rules defined beforehand, and does not change because of one trading session.

It applies to those who run companies, too. A dollar at R$5.00 on a given day is no reason to renegotiate an export contract or to buy imported inputs in volume. Cash, currency protection and contract terms are set in advance, precisely so that no decision depends on guessing the market’s mood on a Monday. The lesson holds for the day of euphoria and for the day of decline.