来自《耶鲁大学开放课程：有关食物的心理学、生物学和政治学 第3集 第3集》

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  How in the world would you know this?
  你到底该如何知道呢
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  Well, there are pretty gross ways of estimating these things
  有种非常粗略的估算方法
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  that typically get used.
  而且是通常的做法
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  One is to look at how much of these foods are produced.
  即看看这些食物生产了多少
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  You can take commercial foods, like Wheaties,
  对象可以是麦片那样的商品
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  and go to the manufacturer and try to figure out
  去联系制造商然后估算出
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  how many boxes of these things are produced.
  这些东西生产了多少箱
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  You figure that most of those boxes
  你的计算中大部分食品
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  are being eaten by somebody or another,
  都被人们吃了
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  there's some waste that you might calculate in,
  浪费的那些也要计算进来
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  but there--error gets introduced there trying to estimate that,
  但其中的误差 也要估算出来
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  so you get a number on that.
  最后得出一个数字