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American chip makers have found themselves at the center of the trade war between the United States and China. It hasn’t been pleasant.

The Philadelphia semiconductor index, the closely watched index of 30 semiconductor companies, has fallen about 16 percent in May, its worst monthly showing since the financial crisis, as the growing dispute takes a toll on companies reliant on China for business. Shares of Qualcomm, Micron, Nvidia and Broadcom are all down by even more. By comparison, the S&P 500 is down about 4 percent.