When there is Buy and sell of real shares in the live float Short selling on borrowed shares Naked short selling Naked Short selling shares not delivered So how is the volume bar in the www.bigcharts.com calculated for stocks
I gave up on following volume 10-15 years ago... as "unreliable" about anything. Swing highs are made on high and low volume. Swing lows the same. Believe what you want, won't change the facts... I thought I might be doing you a favor by posting. If you want tell me to "piss off", that's OK.
Back in the 90's there was some squabbling between the NYSE and the Naz over volume reporting. The Naz was reporting more volume than the Big Board so the NYSE complained that the Naz was inflating it's volume reporting by reporting a transaction of 100 shares as being 200 shares in that a buyer bought 100 and a seller sold that 100. I don't really remember for sure, but I think the NYSE started changing how it reported volume as well. I did a quick google, but I couldn't find anything definitive in the first few hits.
Yes, now that I think about it, I think I remember that too. As far as seeing how your data provider is quoting volume, perhaps you could watch a time a sales report and see if it is correlating to what you chart display shows.