What happened to SPX the last time Core Inflation Rate YoY surprised the market?

The last notable Core Inflation Rate YoY surprise to the downside occurred with the February 2024 CPI release on March 12 2024. Core CPI came in at 3.2% versus 3.3% expected. SPX reacted with an immediate 1.1% rally on the print, closing the day up 1.03%. That move triggered a short-covering rally that carried the index another 1.8% higher over the next three trading days.

From an iron condor perspective, this type of surprise typically produces a fast 40-55 point SPX spike within the first 90 minutes. In the ALVH framework we treat these inflation surprises as high-conviction mean-reversion setups once the initial volatility spike is absorbed. The VIX jumped from 13.1 to 14.8 on the print before settling back near 13.4 by close, creating an excellent opportunity to sell the 0-7 DTE iron condor with 45-55 point wings once the first-hour range was established.

Wing-width management rule applied here: after a 1%+ surprise move we widen wings to at least 50 points to give the condor enough room to handle the residual gamma from the headline. Similar downside surprises in 2023 produced average 0.8-1.4% one-day SPX moves followed by 2-4 day mean reversion, making the post-print iron condor one of the higher-probability setups on the calendar.