for an extended period." Low interest rates and growing federal deficits have weakened the dollar.

VOA: special.2009.11.06

The interest rate has units of time, so I have to specify a time period over which I'm measuring an interest rate.

不同时间段有不同的利率,因此我必须在不同的时间段,细化不同的利率

耶鲁公开课 - 金融市场课程节选

I suspect that with the subprime crisis the Fed will be pushing real interest rates down dramatically again and we may be in a period of negative real interest rates again.

我推测,由于次贷危机,美联储会又一次大幅下调实际利率,我们可能会再次进入,负实际利率的时代

耶鲁公开课 - 金融市场课程节选