US Semiconductor Index Down 35.8%, S&P 500 Down 5.7%
Kadoa has published a data set placing the recent US stock market decline side by side with the crashes of COVID-19 and the 2008 financial crisis. Semiconductor stocks have fallen far more than the market as a whole.
On November 6, Kadoa published a comparison that places the recent decline in US stocks alongside past market crashes. As of that day’s close, the S&P 500 was 5.7% below its record closing high. The Nasdaq was down 10.9%. The PHLX Semiconductor Index, which tracks US chip stocks, was down 35.8%. In other words, semiconductors have fallen far more than the broader market.
How far have chip stocks fallen?
The S&P 500’s decline is still in the single digits, but the semiconductor index has dropped more than a third from its peak. Even within the same market, the picture varies greatly depending on which stocks you look at. For investors in US chip stocks, the gap is wide enough that it is hard to judge the situation from the broad market indexes alone.
Kadoa labels the decline that followed the S&P 500’s record close on October 6, 2026 the “AI selloff.” What the data set covers is how far each index has fallen, and how long it has historically taken to reclaim a previous high.
Where does this rank against past crashes?
In past episodes, the S&P 500 fell much further than it has so far. Kadoa calculates the peak-to-trough decline at 33.9% during the COVID-19 period and 56.8% during the 2008 financial crisis. But the measuring points differ. The current 5.7% figure runs through the November 6 close, while the historical numbers measure the full drop to the lowest close of each crash.
The calculations use daily closing prices rather than intraday levels. Kadoa measures the drop from a record close to the lowest subsequent close, and also compares when each index reclaimed its prior record close.
Comparing across long time spans also means accounting for differences in the indexes themselves. The S&P 500 figures use a price index, excluding dividends. For the period before March 1957, Kadoa uses the predecessor index, the S&P 90. The companies that make up the index have changed from era to era as well.
Where can you see the numbers?
The comparison is posted on a web page that anyone can visit. Kadoa says it will update the figures daily. For investors watching semiconductors, the question is whether the gap between the chip index and the S&P 500 and Nasdaq persists from here.
The value of this comparison is in sizing up the recent decline by setting it next to past crashes. What to watch next: the updated drawdown figures, and whether the indexes recover their highs.