I'm going to give you a very important lesson in price action:
1. There are market orders (includes some algos)
2. There are limit orders (includes some algos)
Market orders are the
flows between buyers and sellers and vice versa at the best available price. Limit orders are some distance above and below the best price, or they would be marketable and execute. Prices fluctuate "randomly" when flow is sufficient to keep prices from hitting the limit order book (
which you cannot observe).
Under market efficiency rules, the price of a stock should reflect all known prices. So when new information comes out, it
should look like this:
Instead, in real life, the market "overreacts" to information, and the actual profile of price is more similar to this:
Note: the actual shape of over/underreaction can vary, but the concept is the same
Why does this happen? Well, the last price before new information was the equilibrium where supply met demand at existing information.
With new information, there is a shock to volume (on either the bid or offer), which pushes the stock above and beyond the new equilibrium price.
The return from selling an overreaction is the compensation for providing liquidity in a tight market, which means you are a net seller of a stock that is seeing a spike higher. If you buy, instead, you are assuming that there will be additional momentum in volume.
Going back to this stock:
Here is an analysis of average volume at time, which is useful in seeing what's happening to a stock.
You can see when 1) volume spiked higher, 2) when it peaked, and 3) the gradual decrease in new avat. This tells us that most of the exogenous shock occurred at the start of the day.
Without looking at the stock, I can infer that there would have been a big spike in price (overreaction) followed by a period of decreasing volatility and more stable prices.
Another thing to note-- most trades are crossing in darkpools:
Finally, we review price and volume data:
As expected, it looks like the stock followed the general overreaction function. Stock ends the day just under 20% higher:
Why did volume increase so much?
Well, large investors make decisions based upon an analysis of future cash flows, the value of a security, and how likely a company is to hit its targets.
These are the biggest investors in the company:
- CGP and Grand Decade (China Pharma) own 40%+
- Avidity (ex-Citadel healthcare focused fund)
- Sirtex (medical device company owned by CGP)
If you go back to the value of a security -- it is the sum of future cash flows discounted by present value. The discount rate (and multiple if you're using that) will incorporate the probability of a stock reaching a cash flow number.
In this example, from equity research, we see that an analyst has these probabilities for product success:
And does not expect revenue until 2022:
Well, today's news added information that potentially increased the probability of product success and may speed up their revenue timeline:
Compare that to this list of upcoming catalysts:
Sometimes the market needs time to digest complex news ("the slow diffusion of information"). This might be the situation here, which means we may continue to see elevated volatility until more details about the Merck trial is released.