SPY on August 5, 2024 - Dealer Positioning During the Yen-Carry Unwind

The August 2024 vol spike is the modern reference event for one reason: it was a positioning crash, not a news crash. No recession printed, no default, no war headline - a crowded funding trade unwound and the hedging mechanics did the rest. Which makes it the perfect day to replay through a dealer-positioning lens, because the mechanics ARE the story. One call per timestamp:

curl -H "X-Api-Key: YOUR_API_KEY" \
  "https://historical.flashalpha.com/v1/exposure/summary/SPY?at=2024-08-05T09:45:00"

9:45 ET - Fifteen Minutes After the Open

{
  "symbol": "SPY",
  "underlying_price": 514.13,
  "as_of": "2024-08-05T09:45:00",
  "gamma_flip": 544.03,
  "regime": "negative_gamma",
  "exposures": {
    "net_gex": -10628900150,
    "net_dex": -134709844624,
    "net_vex": 126286000116,
    "net_chex": -6907338
  },
  "zero_dte": { "net_gex": -787480723, "pct_of_total_gex": 7.4 }
}

Three things in this snapshot deserve a slow read:

• Net GEX -$10.6B. For scale: at 15:30 ET on March 16, 2020 - the -12% day of the Covid crash - net GEX was -$2.8B. August 5 opened almost four times deeper into short-gamma territory. The mechanical read: dealers needed to trade about 20.7 million SPY shares against every 1% move, selling weakness, chasing strength.
• The flip at 544, spot at 514. Spot stood 5.5% below the gamma flip - the entire local price range sat in the amplification regime. No stabilizing hedge flow anywhere nearby.
• Vanna at +$126B. The one shock absorber. With positive VEX, the pre-open vol explosion mechanically pushed dealer deltas up - forced buying into the panic. This is the counterforce that "short gamma amplifies everything" narratives skip, and on August 5 it was enormous.

15:30 ET - The Close Approaches, Positioning Gets Worse

{
  "underlying_price": 516.44,
  "gamma_flip": 546.90,
  "exposures": { "net_gex": -11455774488, "net_dex": -116564827523, "net_vex": 85831986265 },
  "zero_dte": { "net_gex": -1637857088, "pct_of_total_gex": 14.3 }
}

Price had stabilized - spot was actually up slightly from 9:45 - but positioning deteriorated: net GEX deepened to -$11.5B, and the required hedge flow grew to ~22.2M shares per 1%. Two details worth noticing:

• The 0DTE share doubled intraday, from 7.4% of total gamma at 9:45 to 14.3% by 15:30 (-$787M to -$1.64B). Same-day options piled into the stress and made the last hour twitchier - a dynamic that simply did not exist in 2020, when daily expirations were not yet listed.
• The vanna cushion shrank from +$126B to +$86B as vol came off its highs - the morning's mechanical buying support faded into the afternoon.

The End-of-Day Board

From the full summary replay at the close: VIX finished at 38.57, up 64.9% on the day (after printing into the 60s pre-open), VVIX at 173, the VIX term structure in backwardation (VIX9D 42.8 over VIX 38.6 over VIX3M 33.7), and the 1DTE 25-delta skew at 6.8 vol points. SPY closed at 517.42 with ATM IV at 32.6 against a 20-day realized of just 10.5 - a 22-point volatility risk premium, the options market refusing to believe the calm of the prior weeks would return. The put wall sat at 500 with 643,000 puts of open interest - the largest single-strike position on the board.

What This Day Teaches

• Depth of negative GEX ≠ size of the price move. August 5 printed 4x deeper GEX than Covid's worst day, but closed -3% versus -12%. The difference was the +$126B vanna offset and the speed of the vol round-trip. GEX sets the amplification coefficient; the shock still has to arrive through it.
• Positioning can worsen while price recovers. The -$10.6B to -$11.5B deepening during a stabilizing tape is why the following sessions stayed violent even as headlines faded.
• 0DTE is now a stress accelerant. The doubling of same-day gamma share into the close is a structural feature of every modern vol event - visible only at minute resolution.

Replay It Yourself

Related Articles

• Did Hedge Flow Predict the Move? - the same week replayed as a pre-registered 553-stamp flow study
• SPY March 16, 2020: The Covid Crash Replay - the -$2.8B benchmark this day quadrupled
• SPY April 7, 2025: The Tariff-Shock Replay - the next entry in the event library
• VIX Term Structure Inversions Since 2018 - August 2024 as one episode among 37
• 12 Things You Can Do with FlashAlpha Historical

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Frequently Asked Questions

August 5, 2024 is the cleanest specimen of a positioning event in the archive: the deepest short-gamma print of the modern era, a nine-figure vanna cushion doing exactly what the textbook says it should, and 0DTE gamma doubling into the close - all measurable, minute by minute, in the same JSON your production code already parses. The Covid replay shows what negative gamma does to a real catastrophe; this day shows what it does to a purely mechanical one. Both are one at= parameter away.