Quote from alanm:
I don't understand why matching the opening price is any different than going through it. That is, for a 90K opening at a zero-plus tick of 80.50, are not all 6 of these orders guaranteed a fill?
Buy 200 MKT OPG
Buy 200 LMT 80.50 OPG
Buy 200 LMT 81.00 OPG
Buy 200 MKT DAY
Buy 200 LMT 80.50 DAY
Buy 200 LMT 81.00 DAY
Now, if your puny order causes the spec to push the opening price to 80.51, then it is obvious that your LMT 80.50 orders don't get filled. Other than that, though, if the stock opens at 80.50, how can you not get filled?
I believe I have the answer to your question. I will state it in the form of an argument, so that you can SEE it, rather than read it.
Let's simplify by assuming that shorts and longs are treated symettrically and identically, without any tick tests or other short-selling restrictions. Suppose we have the following buys and sells, getting ready for a single price opening:
BUY 100 LOO 80.51
BUY 100 LOO 80.52
BUY 100 LOO 80.53
BUY 100 LOO 80.54
BUY 100 LOO 80.55
BUY 100 LOO 80.56
BUY 100 LOO 80.57
SELL 100 LOO 80.51
SELL 100 LOO 80.52
SELL 100 LOO 80.53
SELL 100 LOO 80.54
SELL 100 LOO 80.55
SELL 100 LOO 80.56
SELL 100 LOO 80.57
Now ask yourself, where should the specialist open? The answer is 80.54, at which a total volume of 400 shares can transact at the open. You can verify for yourself that at any other price, the total volume which can execute will be less than 400 shares, so that 400 shares is the optimal opening price.
Now let's make a small adjustment. Let's add one more order to the scenario, as follows:
BUY 100 LOO 80.54 {order sent by alanm}
Note that we now have 200 shares of buying interest priced at 80.54.
Now ask yourself, where should the specialist open? The answer is still 80.54, at which a total volume of 400 shares can still transact at the open. You can once again verify this for yourself. But here is the problem. Where is the liquidity contra to the extra 100 shares of buying interest which we have just added to the scenario? The answer is that there is no such contra liquidity, there is no such selling liquidity. This means that from among all the buying interest priced at or above the single priced open of 80.54, SOMEBODY has to get stuck without a chair when the music stops playing. Who is that someone? Well, by the rules of price priority, it must be one of the people who is trying to buy at the lowest possible price from among the competitors. This leaves two candidates: alanm's order to buy 100 shares, OR the similar order for 100 shares, submitted by the guy who got there first.
The guy who got there first wins. He gets executed. You do not get a fill.
I agree with cstu that the single priced open is one of the fairest procedures at NYSE.
If you understand all of this, then I suspect you will start to entertain greater doubts as to your use of the concept of "marketable" in the context of a single-priced opening or closing print.