Net Delta-Adjusted Gamma Imbalance

What Is Net Delta-Adjusted Gamma Imbalance?

Net Delta-Adjusted Gamma Imbalance (NDAGI) is an advanced derivatives positioning metric that quantifies the net gamma exposure held by dealers and market makers, adjusted for each option's delta and open interest. Unlike raw gamma exposure, which treats all options as equal in terms of directional impact, NDAGI weights each position by how much that contract is currently 'in play' — i.e., how sensitive it is to small underlying moves. The result is a signed dollar figure (often expressed in millions or billions of dollars of notional gamma) that indicates whether dealers, in aggregate, are net long or net short gamma across the entire volatility surface. When dealers are net long gamma, they act as natural stabilizers by selling into rallies and buying dips. When net short gamma, they must chase price in the direction of movement, amplifying intraday moves and expanding realized volatility.

Why It Matters for Traders

NDAGI has become a core tool for systematic macro and volatility traders because it provides a mechanistic explanation for why markets sometimes trend violently while at other times are pinned to tight ranges. A deeply negative NDAGI reading signals that dealers are structurally short gamma and will be forced to delta-hedge by buying as the market rises and selling as it falls — a pro-cyclical feedback loop. Conversely, positive NDAGI regimes, often coincident with elevated put-selling by retail and institutions, create mean-reverting, low-volatility price action. Equity index traders watch NDAGI alongside implied volatility levels and zero-day options (0DTE) flow, as the explosion of daily-expiry options has dramatically shrunk the time window over which gamma imbalances resolve.

How to Read and Interpret It

NDAGI is typically expressed as a net dollar gamma per 1% move in the underlying. Key thresholds to watch:

• Above +$1 billion per 1% move: Strong positive gamma regime — expect mean reversion, tight intraday ranges, and suppressed realized volatility.
• Near zero: Transitional zone; small catalysts can flip the regime quickly.
• Below -$500 million per 1% move: Dealers are net short gamma; expect trend days, gap risk, and elevated intraday realized volatility. NDAGI spikes negative most reliably around major macro events — FOMC decisions, CPI prints, and options expiry — when dealers accumulate short-dated short gamma from hedgers buying event protection. After expiry, gamma imbalances typically reset, often causing sharp reversals in volatility regime.

Historical Context

During the February 2018 'Volmageddon' episode, NDAGI estimates across S&P 500 options collapsed to approximately -$2.5 billion per 1% move in the days following the spike in the VIX. Dealers who had sold volatility through inverse VIX ETPs were caught net short gamma on an enormous scale, forcing aggressive delta-hedging that turned a modest equity drawdown into a single-day decline of over 4% in the S&P 500 on February 5, 2018. Similarly, in March 2020, as COVID-related put-buying overwhelmed dealer balance sheets, negative NDAGI readings helped explain why a 3%-4% down-gap one morning could extend to 7%-9% intraday without apparent incremental news.

Limitations and Caveats

NDAGI estimates rely on assumptions about who is on each side of every options trade — typically inferred from whether a trade was executed at the bid or ask — and these assumptions can be wrong, especially in fast markets. The rise of 0DTE options complicates NDAGI modeling because such contracts expire within hours, making their gamma contribution highly path-dependent and difficult to aggregate meaningfully at market open. Additionally, NDAGI ignores vega and vanna exposures, which can matter as much as gamma in vol regime transitions, and it says nothing about correlation risk across asset classes.

What to Watch

• Daily NDAGI prints from providers like SpotGamma or SqueezeMetrics relative to key S&P 500 strike clusters.
• NDAGI flip points around monthly and quarterly options expiry dates.
• Interaction between NDAGI and VVIX — when both signal stress simultaneously, vol regime shifts tend to be sharpest.
• 0DTE volume as a share of total SPX options volume, which modulates how quickly NDAGI can shift intraday.