NEW YORK, Aug. 29 -- By the time Kevin Warsh finished speaking in Jackson Hole on Friday, the most crowded trade in America had a new problem. The S&P 500, which has built roughly a third of its entire market weight on technology stocks over the past three years, was staring at the prospect of a Fed chair who is not finished tightening.

The index closed the week up 0.5%, its third consecutive weekly advance, a number that flatters what was, beneath the surface, a more complicated session. Friday's close came down 0.3%, with the Warsh speech delivering a message that carried no rate cut signal and a public commitment to fighting inflation regardless of market discomfort. The 10-year Treasury yield settled at 4.679%. The probability of a S...