Why so long to calculate the S&P 500 closing?

[FSU]

Sig, My feed showed the final closing price at about 3:06 ct. Since the number is based on the final closing price on all the SPX stocks, there may be some stocks who have a late print, so these numbers are not know until all the stocks have actually had their closing prints.

I have seen cases where there is a final print that changes the index price as late as 3:30 ct.

 

[Maverick74]

Sorry for not being specific, I was talking cash. Thanks for the insight, curious as to why the MOC process can't be automated to take place more quickly? You'd think the specialists could set up algos to figure this all out within a couple seconds, especially since the MOC orders need to be in 15 min before the market closes? I'll admit I have no experience with the behind the scenes mechanics of MOC and am curious to hear from someone who has.

Here is some color on the MOC process. Back in the day when we did this (and my firm was still a going concern), we would get the imbalances on Bloomberg at 3:40 pm eastern time. Say WSM had a 800k share buy imbalance, we would slam the specialist with buy orders and then enter the MOC sale by the deadline. We would get the last closing print obviously hoping for a gap on the close. The specialist is posting the imbalance to advertise there is stock to buy and he/she needs sellers to come forward. Often times the imbalance would not be met. In this example say it comes up 300k shares short. This means the specialist will have to sell stock out of his own inventory to cover the balance. Naturally she wants to be compensated for this risk and therefore has to decide where to print the sale. It's not uncommon for a specialist to literally get on the phone and call WSM and ask them if there is anything going on. They often called the DPM's in the options markets as well. This all takes time. Usually they will settle a price quickly but if there is news out it can take longer. They want to set a fair price to be compensated for the risk. But they don't want to over do it. We made life living hell for these guys back in the early 2000's.

 

[SunTrader]

Did the same at Bright.