Just noticed this. Not a technical error. I've seen the same thing in CNN as in TDAmeritrade. Can you explain?
What's SPX.X? I can't find it at my broker or even on Google. SPX itself is an index, so doesn't have volume.
Yeah the S&P 500 index. I think it's the overall volume of all the stocks making up the index. It more than doubled in late 2016 and continued onwards.
Indexes don’t have volume. S&P 500 index doesn’t have volume. I don’t believe the market/trading volume has doubled since 2016. Why make misleading statements and then ask why? Do you also ask why God exists without presenting any evidence?
I don't use Tradingview much so don't know my way to navigate around the website, but here they show volume. https://www.tradingview.com/chart/?symbol=SP:SPX Some indexes indicate volume, but often delayed, ie only after close of market. Norgate data often have volume on some indexes.
Index cannot be traded and cannot have volume. So what would that volume correspond to? S&P futures volume? SPY etf volume? Individual stocks/constituents volume? Would all those volumes combined be meaningful? Or only one/some of them? I’ve looked at SPY volume and it doesn’t seem different. That’s why making statements (by the OP) without any supporting information and then asking “why?” seems looney to me.
With Amibroker/Norgate data which I had for many years, I'd always assumed index volume was as you mentioned, total stock constituents. But never dug down deep to find out as it wasn't important to me. With Commsec broker in Australia, they have index volume but only after mkt close. Barcharts.com don't display index volume.