The United States initiated Operation Epic Fury against the Islamic Republic of Iran on Saturday, 28 February 2026. The S&P 500 (Index: SPX) had closed its trading week the day before, ending at a value of 6,878.88. Through the close of trading on 30 March 2026 the index has dropped 535.16 points, or about 7.8% of its pre-geopolitical event level.
As major events go in the U.S. stock market, at this point in time, the impact of the Iran war is a little smaller in magnitude than 2025's DeepSeek AI shock that sent the S&P 500 crashing between 19 February 2025 and 13 March 2025. The following chart shows both events, with the S&P 500 mapped against its underlying trailing year dividends per share.
The main difference between the two events is the apparent steepness of their declines. As shown in the chart, the DeepSeek AI shock appears to have involved a more severe dropoff, falling a similar amount in a shorter period of time, but we won't know for sure if that's the case until after SPGlobal finalizes the S&P 500's dividened data for 2026-Q1 after the close of trading on 31 March 2026. In the chart, the trailing year dividend data is based on a combination of historic outcomes and quarterly dividend futures that don't precisely match up with the S&P 500's calendar quarters.
In any case, the Iran war event looks set to become larger in magnitude than the DeepSeek AI shock. Will the S&P 500 continue declining so much that it overtakes the combination one-two punch of 2025's DeepSeek AI shock and the "Liberation Day" global tariff event? Or will it recover before it might drop that much?