It's this simple: use the trade date to determine which year you have gains or losses from sales of stock. When you're closing a short sale, use the settlement date for losses but the trade date for gains."
This means that there would be tax selling for those who have losses they want to use for 2013 through Tuesday.
For shorts who want to take losses they must cover by today, but if you want to defer your gains to 2014, you wait until Thursday.
On average SODA is up for the year but short term losses have been high for last half, so I'd expect tax selling through Tuesday. Shorts have profited lately so i'd expect them to put off covering until Thursday. So, Thursday should be a substantial up day as pretty much all sales pressure will be gone by then.
On the other hand, in anticipation of big gains Thursday, some shorts will cover now and buyers may come in before the price shoots up. beginning to sound like the Princess Bride, no?
I would think their are few Soda sellers in terms of tax losses. Because of the flucuations with Soda, people will buy and sell often and wash sale rules would restrict any benefit. But people could be selling managing their profits as it relates to their tax situations.