As the 10-year yield hit a 19-year high, decliners outnumbered gainers three to one and utilities headed for a 19-month low. More than half of the index's members now trade below their 200-day moving averages.
The S&P 500's 0.7% decline on Wednesday looked modest. The market underneath it was in worse shape.
By early afternoon, 304 of the index's 503 components were losing ground, and declining stocks on the New York Stock Exchange and Nasdaq outnumbered advancers by more than three to one. More telling, 258 members, or 51%, were trading below their 200-day moving averages, a widely watched measure of long-term trend. The index itself was still 7.4% above its own 200-day average.
A cap-weighted index can hold well above its trend line when its largest members are strong, even as the typical stock in it slips below its own.
Rate-sensitive sectors fell hardest. The 10-year Treasury yield rose to about 5.13%, its highest level since July 2007, after a strong business survey and a Fed governor's call for further rate increases. Utilities were the worst-performing sector, falling about 1.7%. The State Street Utilities Select Sector SPDR ETF dropped about 1.8% toward a 19-month low, with 30 of its 31 holdings lower. The fund was headed for its ninth loss in 11 sessions, a stretch in which it has fallen 8.3%.
Utilities are often held for their dividends, and when Treasury yields rise, those payouts compete with a risk-free alternative that is paying more. Homebuilders, which depend on mortgage affordability, also fell, with the State Street SPDR S&P Homebuilders ETF down about 1.6%.
Consumer discretionary and communication services lost 1.5% and 1.4%, respectively. Nine of 11 sectors declined. Only energy, up about 1.1%, and industrials, up about 0.2%, gained.
Financial stocks showed how the day turned. The State Street Financial Select Sector SPDR ETF rose as much as 0.5% in the morning as yields climbed, then slipped back into the red. It had fallen 2% on Tuesday to its lowest close since July 1.
Bonds had a rough session of their own. The iShares Core U.S. Aggregate Bond ETF was on pace for its lowest close in more than two years.
A few large Dow members cushioned that index. Boeing, IBM, Salesforce and Chevron all rose, and the Dow Jones Industrial Average fell about 0.6%, less than the Nasdaq Composite's 1.1% decline. The Nasdaq had closed at a record on Tuesday after a four-day run.
Breadth readings like Wednesday's can reverse quickly, and one session does not set a trend. The number to track is the share of S&P 500 members above their 200-day averages. If it keeps falling while the index holds near its highs, the market's gains will rest on a shrinking group of stocks. If it recovers, Wednesday's selloff will look like a rate scare rather than a turn.