Three different things are called “the Nasdaq”.
Graham Says touches the exchange, the Nasdaq Composite and the Nasdaq-100. Keeping them separate is essential.
The same word can mean different things.
Nasdaq is the electronic stock exchange on which listed companies trade.
The broad Nasdaq-listed equity index. Graham Says forecasts its closing level (IXIC).
A narrower large-company index. The NQ futures contract used by the model is written on this index.
The target and predictor track different portfolios.
The two indices overlap heavily in their largest constituents, but they need not move one-for-one. A correctly measured Nasdaq-100 futures move can therefore fail to carry through to the Composite in the same proportion.
The two indices can move together without moving by the same amount.
The Nasdaq-100 and Nasdaq Composite often move in the same direction, but they are not identical portfolios. Graham Says therefore treats cross-index divergence as a genuine source of forecast error rather than assuming it is negligible.