Interest in stocks and options

Short interest helps assess stock sentiment; open interest, an option's volatility.

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How are investors feeling about this market? A mostly sideways moving market since early September might suggest there is some uncertainty—particularly in advance of the forthcoming US elections as well as the lingering COVID-19 pandemic. An uneven recovery for global markets may hinge in large part on further policy support and support from central banks while the pandemic continues to impact economic activity. These factors and more have many active investors trying to figure out where the market goes from here.

Doing your fundamental research is always the first key step in the investing decision-making process, and when it comes to assessing market sentiment, you might also consider adding a few indicators. Here, we focus on 2 technical indicators: short interest for stocks and open interest for options.

What is short interest?

Short interest is the number of shares of a particular stock that have been shorted. An investor who is short may potentially profit if the price declines. It can be considered bearish for a stock to have high or rising short interest.

Short interest is commonly expressed as a percentage—the number of shares sold short divided by the total number of outstanding shares. Suppose there are 10 total outstanding shares of a hypothetical stock. If one of those shares is sold short, the short interest as a percentage of outstanding shares will be 10% (1 ÷ 10 = 10%).

Short interest can also be applied to an index, such as the S&P 500 (or a comparable benchmark), to provide a sense of bearish sentiment for the broad market. The short interest chart below of the SPDR S&P 500 ETF Trust (SPY), which attempts to track the performance of the S&P 500, demonstrates how short interest has trended higher over the course of the year.

Short interest (blue line in the chart above) has declined dramatically since the early spread of COVID-19 in the US. However, it has started to tick higher since mid-September.

While you can get a general sense of investors who are bearish on the market using short interest as applied to an index or comparable security, this measure is more commonly used for individual stocks. If a relatively large percentage of short interest exists relative to similar stocks or to the stock’s own historical levels, it may indicate that sentiment is generally pessimistic for the stock. For example, if stock A and stock B operate in the same industry, and stock A has short interest of 20% while stock B has short interest of 5%, based only on this indicator, market sentiment for stock A may be considered more bearish.

Why you might care about short interest

As with most technical indicators, short interest is not meant to be used in isolation. Rather, investors can use short interest to quickly compare sentiment between stocks and allow for the evaluation of the trend in sentiment for any single stock as well.

Of course, the amount of short interest does not dictate how a stock will perform. Many companies that have a relatively high amount of short interest can exhibit positive returns.

Moreover, short interest can be a double-edged sword. Consider the so-called short squeeze, which occurs when the price of a stock with a relatively high amount of short interest increases at an unexpectedly fast pace. If the stock is consistently moving higher, and short sellers no longer believe it will decline in price, they may decide to cut their losses and close out their short positions by purchasing the stock. This action can result in temporarily “squeezing” the price higher. If you have a short position (which is a risky strategy in and of itself because the potential loss is theoretically unlimited), the potential for a short squeeze is an even bigger risk to consider.

Many traders will also look at "days to cover" to evaluate a stock’s short interest. Days to cover is short interest divided by average daily volume. This can be important because it attempts to measure how long it may take to close out short positions and, consequently, the potential price impact of a short squeeze.

In sum, short interest can serve as another piece of information to assess a potential investment. You should not invest based solely on short interest; however, you can use it to help assess sentiment for a particular investment.

What is open interest?

For options investors, a useful tool to estimate volatility is open interest, which is the total number of options contracts that have not been exercised, closed out, or expired. This differs from volume in that open interest increases when a position is initiated and it decreases when the position is closed out; whereas volume will increase in both instances.

For example, suppose you bought a call option on the S&P 500 Index. This contract is now “open” and, consequently, open interest will increase. If you were to exercise that option one week from today, the contract would then be closed and open interest would decrease.

Meanwhile, volume would increase when you purchased the option and when you sold the option. Thus, you might think of open interest as a measure of active and open positions, and volume as reflecting total trading activity.

The options screenerLog In Required can help you identify options with a certain level of open interest, including those in the Market Scanner provided by LiveVol, a third-party independent research company. LiveVol and Fidelity Investments are independent entities and are not legally affiliated.

This screen attempts to identify options with underlying investments that have open interest at least 300% above their historical average. For example, here is a list of the top 10 stocks or exchange-traded products whose options have the highest percent average open interest that is at least 300% above their historical average, as of October 27, 2020.

  • IGM Biosciences (IGMS)
  • Sunnova Energy International (NOVA)
  • Velodyne Lidar (VLDR)
  • Vaneck Vectors Pharmaceutical ETF (PPH)
  • American Renal Associates Holdings (ARA)
  • LivaNova (LIVN)
  • Kensington Capital Acquisition (KCAC)
  • iShares S&P MidCap 400 Growth (IJK)
  • KE Holdings (BEKE)
  • Multiplan (MPLN)

Why you might care about open interest

Open interest is particularly important for options traders, as it can help measure the potential future liquidity for a particular contract, as well as the potential volatility in the underlying asset. High open interest (and high volume) is a sign of strong liquidity—which is beneficial to options investors. Low open interest (and low volume) may be a sign of weak liquidity.

High open interest can also indicate the potential for volatility. If open interest were to suddenly spike, for instance, it might indicate investors’ belief in the potential for a short-term increase in the underlying stock’s volatility. The reason is that an increased amount of shares controlled by open options contracts might result in future price moves in the underlying stock—if the options are exercised.

Note that a sudden increase, or decrease, in open interest does not necessarily suggest which direction the stock might move. Rather, it may simply indicate there could be a change in the level of volatility. A change in the level of volatility could impact your decision to use different option-related strategies, such as choosing to establish long straddles and strangles for periods of expected high volatility, or butterflys and iron condors for periods of expected low volatility.

Still, some chart analysts think increasing open interest can be used to confirm an increase or decrease in the price of a stock or index. A rise in open interest coinciding with a rise in the price of a stock or index might be due to an increase in long positions (e.g., call options). This could be viewed by some as a bullish signal. Alternatively, if the price is moving higher or lower, but is not confirmed by an increase in open interest as well, that divergence could potentially be a signal that the bullish or bearish momentum may not continue.

To evaluate open interest, you can compare a current level of open interest to previous levels, or you might assess current open interest relative to the volume of contracts traded.

Next steps to consider

Find stocks

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5-step guide to trading

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Technical indicator guide

Learn about more technical indicators and how they can help you trade.

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