The Fed has not tried to influence long-term rates this way since the nineteen sixties.

VOA: special.2009.03.20

These are long-term government bonds and I--now these are--since they're long-term, they have some uncertainty and variability to them.

这些是长期政府债券,由于它们是长期的，就存在不确定性和变化性。

耶鲁公开课 - 金融市场课程节选