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Open Interest Monitor - 16 Sep 2025 - SPX deep dive

Options 10 minutes to read
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Koen Hoorelbeke

Investment and Options Strategist

Open Interest Monitor – 16 Sep 2025 - SPX deep dive

Data through market close 15 September 2025

This monitor tracks how option market activity is clustering across US-listed stocks, ETFs, and indices. We highlight where open interest is growing, how skew and implied volatility shape sentiment, and which tickers show signs of institutional interest.

Each edition also features a deep dive on a single name showing unusual flows, rising implied volatility, or proximity to a key event. This week’s focus is on the S&P 500 Index (ticker SPX:xcbf).


Index-option deep dive: S&P 500 ahead of the Fed and quarterly expiry

This week’s spotlight falls on the S&P 500 Index (SPX:xcbf), as traders position for two major events: Wednesday’s FOMC rate decision and Friday’s quarterly options expiration. These often drive heavy volume, sharp flows, and increased sensitivity to dealer positioning—especially in the index complex.

Options pricing signals a ±1% move into Friday.
With the index near 6,616, this implies a trading range of 6,556 to 6,671. A dovish or hawkish surprise from the Fed could push markets outside that zone, triggering fresh options flows. Otherwise, price may be pulled toward this “gravity range” into expiry.

OI clusters reveal two key dynamics:

  • Far OTM protection: Massive put positions remain at the 5,000 and 6,000 strikes (each >250,000 contracts). These likely reflect longer-term hedging rather than short-term trading.
  • Pin potential at 6,600 call: This strike now shows the largest concentration of near-term call open interest, with high recent volume. If volatility compresses after the Fed, this level could magnetise price into expiry.

Put/call ratios confirm defensive tone:

  • On 15 Sep, same-day expiry (0DTE) flow skewed bearish, with a P/C volume ratio of ~1.21.
  • For the 19 Sep expiry, the put/call OI ratio stands at 1.54, reinforcing the market’s cautious posture.

Open interest distribution – expiry 19 Sep 2025

2025-09-16-00-SPX-OI-distribution-19-sep-2025
Open interest distribution for SPX - OI heatmap for 19 Sep expiry shows tall peaks at 5,000P and 6,000P, and a dense cluster at 6,600C © SaxoTraderGO / Pro

What this means for traders:
Unless the Fed surprises, volatility is expected to peak midweek and contract into expiry. This favours strategies like premium selling or short-dated pin setups near 6,600. A break beyond ±58 points could trigger amplified price action, especially on Thursday and Friday as gamma effects kick in.


Top 20 underlyings by total open interest

Below are the 20 most active US-listed option underlyings by total open interest. These represent the areas where institutional traders are concentrated and where liquidity is deepest.

RankTickerNameLastIV Rank (%)Total OI1M OI % ChgOptions VolP/C Vol
1SPXS&P 500 Index6614.38.822.1M6.3%1.9M1.28
2NVDANvidia Corp177.55.219.7M1.5%1.2M0.42
3SPYS&P 500 SPDR660.97.719.3M8.9%3.4M1.08
4VIXCBOE Volatility Index15.46.114.3M14.0%0.6M1.58
5IWMRussell 2000 ETF239.49.213.0M8.6%0.5M0.75
6TSLATesla Inc343.87.112.8M7.5%1.9M0.89
7AAPLApple Inc252.66.611.5M6.2%1.7M0.91
8QQQNasdaq 100 ETF455.35.410.9M7.8%1.2M1.12
9AMZNAmazon.com Inc196.48.910.2M5.7%1.3M0.95
10METAMeta Platforms Inc581.24.79.6M4.3%0.9M0.88
11AMDAdvanced Micro Dev166.76.49.0M5.1%0.8M0.93
12MSFTMicrosoft Corp452.37.28.7M5.5%1.0M1.01
13GOOGLAlphabet Inc-A172.58.08.2M4.9%0.9M0.97
14XLFFinancial Select ETF43.85.97.9M7.4%0.6M1.22
15JPMJPMorgan Chase & Co184.16.27.6M6.8%0.5M1.09
16NFLXNetflix Inc654.97.37.2M6.1%0.5M0.84
17GMEGameStop Corp42.79.16.9M8.2%0.4M0.79
18BABAAlibaba ADR92.38.56.6M7.9%0.4M0.87
19XBIBiotech ETF105.85.06.4M7.2%0.3M1.15
20INTCIntel Corp39.44.96.1M5.6%0.3M0.92

This table shows the 20 listed options with the highest total open interest, combining calls and puts. Open interest data reflects active outstanding contracts and offers insights into market liquidity, sentiment, and positioning.

What the columns mean (short version):

Last = Last traded price of the underlying
IV Rank = Implied volatility rank (0–100 scale)
Total OI = Combined open interest for puts and calls
1M OI % Chg = Change in total open interest over the past month
Options Vol = Daily trading volume in options
P/C Vol = Put/Call volume ratio (based on daily volume)

For more detail, see the full glossary at the bottom of this article.


What traders can take away

Based on the top 100 by open interest

Several underlyings saw notable increases in open interest over the past month, with the largest relative gains concentrated in a handful of names. Chinese e-commerce platform JD.com led the surge with a 41% jump in OI, followed closely by media stock Warner Bros Discovery (WBD) and enterprise software giant Oracle (ORCL), both up over 30%. These moves suggest either speculative positioning or renewed institutional focus as macro and sector narratives evolve. Semiconductor company Wolfspeed (WOLF) and China tech ETF KWEB round out the top five, hinting at thematic plays around AI and geopolitical recovery, respectively.

Volatility expectations are also shifting. WOLF stands out with an IV Rank above 90%, placing it in the top percentile of its past-year range. Elevated IV Ranks in WBD and Boeing (B) suggest traders are pricing in potential catalysts or simply preparing for sharp directional moves. These high IV names often attract premium-selling strategies, especially when combined with elevated OI.

On the sentiment front, the put/call volume ratios offer a useful read. Defensive hedging remains prevalent in the financials and credit space, with KRE, HYG, and SMH all showing ratios well above 1.0. This points to a cautious stance, potentially tied to interest rate uncertainty or credit cycle risk. On the other end of the spectrum, extremely low P/C volume ratios in JD, Core Scientific (CORZ), and EOS Energy (EOSE) suggest speculative call buying or a lack of put demand—both signs of risk-on behaviour in these names.


A few observations

Based on the top 100 by open interest

One clear takeaway this week is the subdued volatility across many mega caps. Despite the looming Fed decision, stocks like Nvidia (NVDA), Meta Platforms (META), and Intel (INTC) all show implied volatility ranks below 10%. This calm IV environment may reflect confidence in the stability of these names or complacency around macro risk—either way, it opens the door for strategies that benefit from mean-reverting price action or short-vol setups.

At the same time, there’s little doubt that downside protection remains in demand. High P/C ratios in ETFs like KRE and HYG confirm that traders are still allocating toward hedges in sectors vulnerable to credit or rate shocks. The persistence of these ratios suggests that this isn’t just short-term event hedging, but part of a broader, cautious rebalancing.

Lastly, thematic flows continue to surface. Beyond the tech heavyweights dominating the OI leaderboard, there's growing activity in biotech (XBI), AI-exposed chipmakers (NVDA, AMD), and Chinese internet platforms (KWEB, JD). These pockets of interest hint at a market that remains selective and narrative-driven, even as headline indices tread water.


Conclusion

Positioning across the options landscape remains concentrated in indices and large-cap tech, but notable activity is emerging in select thematic and event-driven names. The S&P 500 sits at the centre of attention this week, with Fed policy and quarterly expiry combining to anchor flows near the 6,600 level. While implied volatility is subdued in most large-cap underlyings, elevated put/call ratios in financials and credit-linked ETFs point to a defensive undercurrent. Traders appear cautiously constructive—engaged in rotation, but still hedged for macro risks. With volatility likely to peak midweek, the days ahead may favour short-term strategies tied to expiry dynamics and volatility compression.


Glossary

  • Ticker: the exchange-listed symbol for the underlying stock, ETF, or index. Indices are noted with a $ prefix in general use, but we map them to specific exchange codes in the ticker string.
  • Name: the company or ETF name associated with the ticker. ETFs typically describe their focus, such as “S&P 500” or “20+ Year Treasury Bonds.”
  • Last: The last traded price of the underlying asset (stock, ETF, or index). This gives a reference point for where the asset currently trades and helps identify how close it is to key strike levels in the option chain.
  • IV Rank (%): Implied Volatility Rank (IV Rank) shows where current implied volatility sits relative to the past 12 months. A reading of 0% means IV is at its lowest point of the year; 100% means it's at the highest. Higher IV Rank suggests options are more expensive compared to recent history, which may favour premium-selling strategies.
  • Total Open Interest (Total OI): This is the total number of open option contracts across both calls and puts for the underlying. It represents outstanding positions that have not yet been closed or exercised. High OI is often associated with deep liquidity and significant institutional interest.
  • 1M OI % Change: Shows how much total open interest has changed over the past month. A rising figure can point to fresh positioning or increased speculation, while a falling number may indicate closed-out trades or reduced interest in the underlying.
  • Options Volume: The number of option contracts traded during the most recent session. High volume relative to open interest may suggest new trades are being initiated. Sudden spikes often coincide with market-moving news or upcoming events.
  • Put/Call Volume Ratio (P/C Vol): This ratio compares the volume of puts traded to calls on the same day. A ratio above 1.0 implies more puts were traded (often for downside protection), while a value below 1.0 shows call-heavy flow (often speculative or bullish). Extreme readings can highlight skewed sentiment or potential contrarian signals.
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