When I buy 100 shares, does the trade volume increase by exactly 100 shares?
Suppose there are 4 entities involved in a transaction: me, my broker, dealer A, and dealer B. When I place an order to buy 100 shares, my broker contacts dealer A. Suppose dealer A does not have any shares in stock. Dealer A buys 100 shares from dealer B. Then, dealer A sells 100 shares to me via my broker. As you can see, there were two transactions of 100 shares each. Did this whole process increase the volume by 100 shares or 200 shares?
(Answers need not be specific to the US, but if this is a region-specific issue, feel free to answer about the US stock market)