Is the stock market rebound sustainable with such high concentration?
Core argument: The Philadelphia Semiconductor index surged 40%+ since the conflict began, with Intel and SanDisk each doubling, driving S&P 500 outperformance.
Wall Street’s rebound since late March has been driven by the smallest number of stocks on record, pushing US market concentration to an all-time high and prompting warnings about the “fragility” of the rally. Before the conflict began, the equal-weight version of the S&P powered ahead of the more commonly used index, in which bigger companies are weighted more heavily. But that pattern has reversed during the market rebound, with the S&P, which is dominated by Silicon Valley’s megacap tech companies, performing far better than its equal-weight counterpart. The Philadelphia Semiconductor index has surged more than 40% since the war started, with chipmaker Intel up more than 130% and memory giant Sandisk up 100%.

