The VIX Beta Tracker measures volatility reactivity by calculating the exact number of VIX points added per 1% drop in the S&P 500. By evaluating today's reactivity against its 6-month trailing baseline (Reaction Deviation) and applying a Dual-Variable Matching Protocol (Reaction Quintile + VIX Level), the tracker identifies statistically equivalent historical sessions to project forward VIX spike probabilities across 5-, 10-, and 20-session trading windows.
1. Conceptual Hierarchy
Beta is a rate of reaction rather than a standalone price level. It answers a fundamental question about market behavior during equity down days: when the S&P 500 fell, how aggressively did market participants reprice volatility?
The S&P falls, the volatility complex reprices, and beta is the ratio between the two. A session at 1.70 added 1.70 VIX points for each 1% the index gave up.
VIX Beta = 1.70: Volatility added 1.70 VIX points for every 1.00% decline in the S&P 500 during the session.
High VIX Beta: Indicates a jumpy, highly reactive volatility market where modest equity drops spark outsized VIX surges.
Low VIX Beta: Signals a muted, sluggish volatility response where equity drops fail to stimulate options demand.
2. Baseline System Inputs
The system captures two live inputs from the most recent trading session with a meaningful S&P 500 decline:
Raw VIX Beta changes over time depending on the current volatility environment. To create an apples-to-apples comparison across market regimes, the analyzer subtracts the 6-month baseline from today's raw beta to determine the Reaction Deviation, then ranks this deviation using a Dual-Variable Matching Protocol.
1. Raw Beta Calculation
Raw session beta maps the inverse relationship between the VIX point change and the S&P 500 percentage move:
The 6-month baseline is calculated using an origin-fitted regression across S&P down days over a trailing 21-session window, averaged over 6 months (126 sessions). Subtracting this baseline isolates the true, unusual reactivity of the current session:
A deviation near zero means the session reacted about as the market has been reacting lately. The percentile places that deviation against every comparable past session.
3. Dual-Variable Matching Protocol
Candidate historical sessions must satisfy two independent constraints simultaneously:
Both constraints have to hold on the same session. The quintile keeps the reaction comparable; the VIX filter keeps the starting point comparable.
Why Match on Reaction Deviation Rather Than Raw Beta?
Volatility reactivity runs higher in some macro regimes than others. Subtracting the 6-month average removes slow macro drift and isolates whether today's session was unusually reactive relative to recent market norms. Combining this quintile with a VIX level filter ensures starting baseline points and potential point surges mean the exact same thing across the dataset.
Chapter 3
Cumulative Intraday Spike Probabilities
The Spike Probability Engine evaluates how frequently matched historical sessions touched specific point-expansion thresholds across three forward time frames: 5, 10, and 20 trading days.
1. Intraday "Touch" Logic
Breaches are triggered the instant spot VIX touches or crosses a target level during trading hours. The system does not require VIX to close at or above that level.
Upward Targets: Triggered if the intraday High reaches or exceeds the target.
Downward Targets: Triggered if the intraday Low reaches or crosses below the target.
This path hits the target early in the window and then closes lower than it started. The touch is what gets recorded, so the session still counts toward that level.
Key Execution Rule
Any intraday touch registers as a valid historical breach across all active forward windows (5, 10, or 20 days), even if VIX drops back down before the closing bell.
The Setup Log provides an audit trail detailing every individual historical trading session that matched both search parameters: the Reaction Quintile and the VIX Level Filter.
The Columns
Column Header
Definition
Analytical Value
Date
Historical trading session timestamp.
Shows historical path distribution across macro regimes.
Beta
VIX points gained per 1% S&P decline on that date.
Displays the raw session reaction rate.
Pctile
Percentile rank of that session's Reaction Deviation.
Confirms row alignment with the active setup's quintile.
VIX
Closing spot VIX level on the matched session date.
Confirms starting point compatibility across matches.
Highest VIX Move
Max intraday point expansion above entry across 5/10/20 sessions.
Supplies raw intraday metrics feeding probability calculations.
Interpretation Rules
"Never Went Higher": Indicates that spot VIX did not trade above its entry closing price at any point during the forward window.
Pending Status: Identifies recent historical matches whose 5-, 10-, or 20-session tracking windows are currently ongoing.
Skew Evaluation: Comparing average peak moves against median peak moves reveals whether sample probabilities are driven by a few extreme tail events or broad systemic trends.
Example Skew Analysis
In this matched sample, the median peak 20-day move was +4.45 points, while the maximum peak move reached +47.69 points (from a July 2024 session). Sorting by the 20-day column immediately isolates these extreme outlier events.