美国财政部拍卖四周期国债，得标利率4.220%（5月15日报4.220%），投标倍数2.78（前次为2.91）。拍卖八周期国债，得标利率4.235%（5月15日报4.235%），投标倍数2.89（前次为2.85）。

Group 1 - The U.S. Treasury auctioned four-week and eight-week Treasury bills with a winning yield of 4.220% and 4.235% respectively, indicating a stable interest rate environment [1] - The bid-to-cover ratio for the four-week bills was 2.78, slightly down from the previous auction's 2.91, suggesting a decrease in demand [1] - The bid-to-cover ratio for the eight-week bills was 2.89, which is an increase from the prior auction's 2.85, indicating a slight improvement in demand [1]