China is re-emerging as a major consumer of U.S. cotton after years of stockpiling the fiber, a shift that together with poor growing conditions in Texas has sent prices surging to a six-year high.

The world’s most populous nation has purchased futures contracts covering more than 361,000 bales of U.S. cotton for 2019-20, according to U.S. Department of Agriculture data. That is enough to make 400 million T-shirts. China has never booked that much cotton that far in advance at this time of year, in data going back to 1998.

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