The market closes, then the forecast gets scored.
The target-date forecast remains frozen until the realised Nasdaq Composite close becomes available. Scoring adds the outcome to the record; it does not rewrite the prediction.
The actual close belongs to the scoring stage, not the forecasting stage.
Keeping those stages separate is what makes the prospective record meaningful: the answer is not available when the prediction is created.
How far away was the forecast?
Absolute error is measured in Nasdaq Composite index points. Lower is better.
Percentage error provides a scale-free interpretation of the same miss.
The same chronology every session.
The target-date prediction is already locked.
The realised Nasdaq Composite close becomes known.
Match forecast and actual on the same target date.
Record absolute and percentage error.
Add the scored date to the prospective history.
One forecast tells us very little. A sequence is more useful.
Each new forecast is generated under the same pre-specified rules. As that common sample grows, Graham Says can compare models using mean absolute closing-level error without pretending historical backtests were live forecasts.