Which Mega-Cap Is Carrying the Index: Seven Perps, No Weights

When the S&P 500 perp is up on a Sunday, the next question is what is behind it. An index is its members, and a handful of members account for a large share of both the S&P 500 and the Nasdaq 100. Mega-cap concentration in SPY covers how much they matter in regular hours. On a weekend those names have perps of their own.

The seven

The names are NVDA, AAPL, MSFT, AMZN, GOOGL, META and TSLA. Each has a perp that trades around the clock. Each is measured the way the index perps are: its price now against its own price at the last regular cash close, taken from the candle that ends at the bell. If a name has no print at the bell, it has no figure.

How the list is shown

The seven are listed unweighted, with the largest move first. Sorting by size of move puts the name doing the most at the top, whichever direction it went. You read down the list and see at a glance whether one name stands apart or all of them moved by similar amounts.

Why no weights

An obvious improvement would be to multiply each move by the name’s index weight and show its contribution in index points. The list does not do that, for three reasons.

First, weights are not fixed. They change with every price change, and they differ between the S&P 500 and the Nasdaq 100. A weighted figure needs a weight taken at some moment, and the weekend move itself shifts it.

Second, a weighted contribution is a calculation. The move on each perp is a measurement. Putting a calculated number in the same row as measured ones makes the display look more exact than it is.

Third, the seven perps and the index perp are separate markets with separate depth. Their moves do not have to add up. A table that implied they should would invite a reader to reconcile numbers that were never meant to reconcile.

What the list can tell you

It tells you direction and rough size by name. It tells you whether the index perp’s move has company. If the index perp is up and one name is up several times as much as the rest, the move has a single source. If all seven moved together, it does not. All seven together, or one name alone reads those patterns.

What it cannot

It cannot tell you about the other names in the index, which have no place on the list. It cannot be summed into an index figure. And the same ticker can trade on more than one book, each with its own price, so one name’s perp is one market’s view of that name. The Perps & Futures tab on Trader shows the seven beside the index perps while the cash market is shut.