The Philadelphia Stock Exchange Semiconductor Index dropped 6% this week, on track for the worst month since the financial crisis. The Nasdaq 100 index is off almost 7% from its all-time peak at the start of the month. A gauge of the FANGs, -- Facebook Inc., Amazon.com Inc., Netflix Inc. and Alphabet Inc. -- has fallen faster still.

That’s all vital because the phenomenal performance of tech shares has underpinned the decade-long bull market. From trough to peak the Nasdaq 100 gained about twice as much as the S&P 500.

“Tech, communications and consumer discretionary look to me to be the three areas to avoid now,” said David Holohan, head of equity strategy at Mediolanum Asset Management in Dublin. “The outlook has certainly deteriorated because of supply chain worries particularly on the semiconductor side, and they’re only going to get worse.”

Nor is the pain limited to American shares. The three biggest stocks on the MSCI Emerging Markets index -- Tencent Holdings Ltd., Alibaba Group Holding Ltd., and Taiwan Semiconductor Manufacturing Co. -- are having a miserable month.

The developing world is another of those ugly marks in global markets just now. Alongside a crisis of confidence for foreign investors in Turkey, rhetoric between the U.S. and Iran has been ratcheting up. Money has been fleeing the most-actively traded emerging-market ETF.

The doubts about tech have fed into a broader pessimism on Wall Street. Short interest as a percentage of shares outstanding on the largest S&P 500 ETF jumped as high as 7% this week, according to data from IHS Markit Ltd. That’s the highest level since 2015.

Part of the trigger back then was the prospect of interest rates rising for the first time in almost a decade. The Federal Reserve played its part in the market wake-up call this week, with minutes from the latest meeting showing policy makers in no rush toward easier policy, even as markets price in rate cuts.

There are many who argue moves in the stock market are largely decided by moves in the rates market. Since they both react to the same macro catalysts it’s hard to prove or disprove, but a chart of the S&P 500 and the yield on 10-year Treasuries for Thursday lays bare the close relationship.

Bond yields are marching lower amid increasing conviction that this tightening cycle is over, and the 10-year yield hit the lowest since 2017 in the week.

The heart of all this is not the trade war itself, but its potential impact on global economic growth. A slew of economists at Wall Street’s biggest firms and beyond took a bearish lurch this week, with the likes of Goldman Sachs Group Inc. and JPMorgan Chase & Co. rewriting forecasts for how bad the protectionist showdown will get.