Explanation requested...On interlisted securities........the share volumes are pretty close on both sides with SPX.....yet another stock that I own the volume is considerably higher on the US side ( it is a Can stock ). So with SPX are these the same shares just being shown on two different exchanges....and if so why is there a large discrepancy on other stocks that are interlisted. Another Canadian stock that I own will sometimes trade on the OTC for thousands of shares but 0 on the Canadian exchange.