Have you ever wondered how is it possible that when you buy some shares of SPY someone out there is somehow able to collect 500 securities to fulfil your order? Even if it's not a literal action-reaction, that is what must be happening at the margin.
Also, if you still don't believe me, then try to find out how to unpack X amount of shares of SPY (for some non-small amount of X) into individual securities. Can you do it yourself, for example? Whom to call, where's the button for that, who can do it?
Have you ever wondered how is it possible that when you buy some shares of SPY someone out there is somehow able to collect 500 securities to fulfil your order? Even if it's not a literal action-reaction, that is what must be happening at the margin.
Also, if you still don't believe me, then try to find out how to unpack X amount of shares of SPY (for some non-small amount of X) into individual securities. Can you do it yourself, for example? Whom to call, where's the button for that, who can do it?