Indeed,volatile food prices, population growth, low agricultural productivity and the potentially devastating effects of climate change make it a particularly daunting challenge. The IFAD president says over the past 30 years, agricultural productivity in developing countries has been stagnant or in decline. He blames it on years of under-investment.

VOA: standard.2010.03.29

But then developments in other fields can change the relative prices and suddenly make an idea that had been hypothetical and unapplied suddenly work well.

而其他领域的发展,改变了相对价格,过去那些看似空想,而且不切实际的主意,就突然间变得可行了

耶鲁公开课 - 金融市场课程节选

Of course, this was just a change in stock prices; it wasn't related to any fundamental change in the economy or any fundamental change in corporate prospects.

当然,这只是股价上的变化,整个经济或是各个上市公司,并没有发生根本的变化

耶鲁公开课 - 金融市场课程节选

We have prices of options that change minute by minute.

期权价格瞬息万变

耶鲁公开课 - 金融市场课程节选