For the millionth time, could someone please walk me through how they expect options open interest to affect price action this afternoon?
Using specific numbers with today's expiration would be helpful, and I would highly appreciate it.
I don't recall you asking even once before, let alone a million times. But let me give you my understanding, maybe others will chime in.
(As I write this, 11:40PST,
Max Pain | Maximum-Pain.com shows the following for TSLA:
If the price of TSLA at close in an hour or so is right of the yellow line, the green bar shows roughly what the call options will be worth to the longs holding them. The red bars are correspondingly what the put options will be worth to the holders.
By "holders" I mean the usual investors who buy calls or puts. But someone has to "write" the contracts. While there are people posting here who actually sell options contracts, most of them are written by "market makers", often big banks or hedge funds or whoever, but they have lots of money. The further away from the yellow line it is at close of market, the more money someone else makes, and therefore the less money the market maker makes. Bear in mind that they've usually already made their money from the declining time value of the options, so it isn't that they lose money, it's just that they make less. Still, they want to minimize how much they pay out on their side of the bets; the house (almost) always wins.
So it's in the MM's best interest to manipulate the stock price back towards the yellow line. Reading the graph above, it looks to me like they'll have to pay out about $8M if TSLA closes at $340. But it's currently $354.60 (as I type), that looks to me like about a $14M payout. So if they can sell less than $6M (= 14-8) worth of TSLA and force the price back to $340, they win. That's why volume is so important. On a low volume day they don't have to sell much to do that, but on a high volume day they might have to sell a lot, and even then it might not work. It looks to me like about 14:30EST they decided that even trying to hold the fort at $352.50 wasn't going to work, and they gave up.
Why, you might ask, do they try to stay close to a strike price? Options that are well away from that price are either worthless or worth a lot and a few cents swing in price doesn't matter much, but the people who have $355 puts ($254.88 as I type, pretend it closes at that price) can give their shares to the writer (market maker) in return for $355, but could have bought those shares for just 12 cents less. While there's little money involved, the difference between 12c/share and 24c/share is 100%! Ideal for the market maker is for it to close at exactly $355, in which case both the calls and the puts at that strike expire worthless.
Mod: This should really be in the options trading thread. --ggr