Magna.. im pretty sure you are right about all ecns accepting odd lots.. some ecns will only execute odd lot orders against another odd lot orders though.. INCA for example.. http://www.hardrightedge.com/work/orderrouting.htm -qwik
who the hell buys 108 shares of a stock?????????????????????????????????????? Look who's talking, you bought 8. Once this sort of thing starts, the partials continue until the price moves away and people cancel their orders, and sometimes not even then. Then those who have partials left sell/buy them at the new price level (just like you did) starting the fun all over again. Btw, did you notice that whenever you get a partial your order drops as many price levels on level2 as necessary for it to again qualify for inclusion? Here's what I mean: Let's say the level 2 shows bid at 90.0 and ask at 90.2. You put in an order to buy 100 shares at 90.0. Let's say your order is the only ISLD order at that price. Someone buys 8 shares from you. You now have a bid for 92 shares and you no longer qualify for inclusion on level2 at the price of 90.0, so now ISLD will add your 92 shares to 8 shares from a bid at a lower price (for example 89.98) and now your remaining 92 shares are displayed on level2 as a part of a 100 share bid at 89.98. The same thing happens if there are many people bidding at the same price, it just that it happens to whoever is last in the queue. If you are the last in the queue of six people, each of them with a 100 share bid at 90.0, someone needs to get rid of his partials and sells 8 shares at the bid, ISLD now can no longer display 600 shares at 90.0 (since it only has 592 at that price) so it will take 8 shares from you and display that as part of the max. 500 shares that it can display at 90.0, and your remaining 92 shares will again be added to a lower ISLD bid and displayed at the lower price. Again, the same thing happens when someone bids an odd lot at a price higher than your bid. Six people bid at 90.0, you are the last one in the queue. Someone bids 90 shares at 90.01, since it's an odd lot the order can't be displayed at it's price, it gets dropped to 90.0. This order is at a higher price so it goes to the front of the queue, 90 shares of your order get dropped to whatever is the lower bid. Keep in mind that someone can get in front of you in the queue by sending an order with bid price that would not be allowed on level2 because it's not a multiple of the increment for that issue. ISLD allows trading at a smaller increment. When you have the only bid at 90.0, your bid is for 100 shares and you see the ISLD bid on level2 increase by 400 shares, technically these people could be in front of you in the queue, if they bid at 90 and 1/1024th or whatever increment ISLD allows these days. The last thing is unlikely to happen often, especially now that we have a 1 cent increment. The previous three scenarios happen all the time. You can see it on level 2 if you watch for it. This only matters when the following happens: 1. Either an automatic system (either a trading system, a broker with some special routing algorithm such as IB's Best ecn or another ecn such as ARCA) or a trader would make their trading decisions based on the amount of shares ISLD displays on level II. For example if ARCA is trying to fill an order to sell 600 shares at 90.0, seeing 500 shares available at 90.0 (even though there is 592) would get the 500 shares from ISLD and look for the rest somewhere else. 2. If you are on the other side of the example above, it's your 600 share order on ARCA but the order is to sell at 89.98. ARCA might get all 600 shares from ISLD, but even though there is 592 shares available at 90.0 ARCA using selectnet would get the prices shown on level2. It would get 500 shares at 90.0 and 100 shares at 89.98. I'm pretty sure neither side of the trade get's a price improvement, the $1.80 difference between what is shown on level2 and the actual bids goes to ISLD. So you see, partials are probably quite profitable for ISLD. voodoo
I wrote above that an ARCA order for 600 shares at 89.98 would get 500 shares from ISLD at 90.0 (even though there are 592 available at that price) and 100 at 89.98, in other words it would get the prices as shown on level2. I don't believe that is correct any more (if it ever was,) since ARCA gets shares directly from ISLD, and does not use Selectnet (I just checked an order routing table.) I still believe (but am not sure) that anyone using Selectnet would get the prices shown on level2, and that the other side would not get a price improvement, which would mean that ISLD would pocket the $1.80 difference. voodoo