yahoo SPX volume is just weird

https://finance.yahoo.com/quote/^GSPC/history?p=^GSPC

Does anyone understand why the historical reported volume for SP500 on yahoo is much higher than everyone else's ? What are they reporting differently?

 

What is "GSPC."
In your question, you wrote "SPX", which is a cash index.

What S&P symbol are you looking for volume on?

 

yahoo uses the ticker GSPC for SPX for whatever reasons
so they are the same

 

But you can't trade SPX as symbol, so where is the volume generated from?

 

Do you think they are adding up the volume from the 500 stocks?

 

CNN's site has the same number listed for yesterday's total volume...?

http://money.cnn.com/data/markets/sandp/

 

Huh! I haven't done this in a while but, googling
"S&P500 volume"
produces a boatload of hits.

So, aside from "It's an index; doesn't trade."......
the various formulations
(additive shares, price-weighted shares, capitalization-weighted shares, whatever) all seem to have adherents.

Wish I had more time.

 

Good lord I too googled this and gave up trying to find it. I would assume its calculated in the same way as the index - market weighted - so for each stock in the index you take its volume that day, multiply it by its weight in the index, then add all of those 500 calculated amounts together. But nothing immediately popped up showing it. Weird. Have we just come upon a flaw in the matrix?

 

Why not try aggregating the volume of all 500 companies on the S&P to figure out the volume of the S&P index?

Why does it have to be so complicated? VWAP has to do with price, but volume has nothing to do with price? Volume is volume. It is factual, not "calculated". It is not averaged. It is what it is.

Just add up the total number of shares traded on each of the 500 companies that make up the S&P 500 index. That would be the total volume of the S&P index, yes? (This doesn't include options I would reckon', because options are not shares traded. If options are exercised, then yes, but then those shares would just be in the total number of shares traded.) *shrugs*

 

Sure, you COULD just add them up. Maybe they do that. But the goal, I would think, is to figure out what the volume of that index would be if that index were a real thing you could by or sell. And, if so, I maintain that the representative volume of that index would be calculated as I indicated. Why would you measure volume in a way that is not consistent with how you are determining price? I dunno, maybe they are just adding them up, but that would seem weird to me.