Tesla is one of the most volatile large cap stocks in the market. It's a battleground stock with the war between longs and shorts waged in each buy or sell order, and each resulting fluctuation of its stock price. In about a year the price has gone from $377 in December 2018, halving to $177 in June 2019, subsequently tripling to close at $525 most recently on the 13th of January 2020.
The stock war is waged not just in the direct purchase or sale of the stock, or in the media, but in the options market too, where insufficient attention is paid by the ordinary investor, and where much descriptive value may be found. The options market can exhibit reflexivity, a circular relationship between cause and effect. The strike price of price of an option can act as a magnet pulling the underlying stock price, creating a virtuous, or vicious, cycle depending on where you have placed your own bets. The options activity in Tesla is unique in several respects, and understanding this will aide understanding of the volatility in the underlying stock price.
According to the Options Clearing Corporation the open interest in put options on Tesla stock amounted to 160 million units on the 13th of January. This is more than the number of shares in Tesla's float, an unusually large number of open options that suggests a large degree of influence over the underlying stock. There were 80 million call options on this date for a 2:1 Put-Call ratio. This is in contrast to an approximate 1:1 Put-Call ratio across the market and suggests a high degree of bearish sentiment toward Tesla stock.
Two of the key factors in the relationship between a call or put option and the underlying stock price are the strike price of the option, and the expiration date. This is where two important facts will emerge.
1) Most put option volume on Tesla stock is currently deep out of the money, and most call option volume is in the money, as the following volume chart segmented by option strike price reveals:
2) Nearly half of call and put option volume expires on the 17th of Jan, as the following volume chart segmented by option expiry date reveals:
Combining the above facts under the assumption that counterparties have hedged their exposure, we can determine what has been the impact to the underlying stock demand of these contracts, and how this might change in response to changes in the underlying stock price. Options pricing theory provides just such a mechanism - Delta Hedging. For our purposes the most important thing to know about Delta Hedging is that the more likely an options contract is to be exercised, the greater the number of underlying shares the counterparty to that contract needs to transact in to hedge their exposure.
The same options pricing theory that provided us with Delta-Hedging, the Black-Scholes model, also provides a mechanism to calculate the value of the call and put options, and the calculated values of these options track closely to recent trade prices of those options. This implies this is not simply a theoretical exercise but has some basis in reality with regards to the any underlying share transactions to offset the exposure on these options, and the observed activity in Tesla stock.
It's important to recognise that the number of shares required to offset an options position is not static and changes, most importantly, with the price of the underlying stock. The following chart shows the Delta Hedged volumes segmented by different underlying stock prices:
The actual stock price increase of $47 on the 13th of Jan is enough to stimulate demand for nearly 17 million shares of Tesla stock, more than the single largest institutional investor in Tesla, Baillie Gifford, has accumulated, and all in a single day. This reflects a virtuous (or vicious) cycle where a stock price increase induces further demand for Tesla stock which all else equal will push the price up further as further counterparty share purchases are required to offset their options exposure. The reverse is also true, as a reduction in the share price would have the exact opposite effect. This self-reinforcing cycle explains the volatility and periods of momentum we have seen in Tesla stock to a significant degree, but there are caveats. There will be differences in timing and extent to which counterparties hedge their exposure. And other factors influence the stock price too, principally market participants deciding whether to continue to participate, or to place their chips elsewhere.
[Disclosure: long time holder of Tesla stock]