BlockBeats News, August 20th, as the yield on U.S. Treasury bonds rose rapidly, one or more investors significantly increased their holdings in a U.S. Treasury ETF highly sensitive to long-term interest rate changes the day before the Treasury announced an expansion of its repurchase size.

The $1.5 billion PIMCO 25+ Year Zero Coupon U.S. Treasury Index ETF (ZROZ) received a net inflow of $123 million on Tuesday, marking a historical high for the fund; the trading volume reached 5.2 million shares, nearly twice the previous high set in 2024.

ZROZ mainly invests in Separate Trading of Registered Interest and Principal Securities (STRIPS), which are zero-coupon securities created by separating the principal and interest payments of Treasury bonds. The fund has an effective duration of about 28 years, meaning that if the yield were to drop by 1 percentage point, the bond's price would theoretically rise by about 28%. Therefore, it is essentially a tool with high sensitivity to U.S. long-term interest rate changes.

The fund rose 3.2% on Wednesday, marking its largest single-day gain since November 2024.