Sub-zero interest rates are neither unfair nor unnatural.

　　负利率既非不公平也非不自然。

　　DENMARK’S Maritime Museum in Elsinore includes one particularly unappetising exhibit: the world’s oldest ship’s biscuit, from a voyage in 1852.

　　丹麦的埃尔西诺航海博物馆藏有一件特别让人没有胃口的展品：世上最古老的船员干粮，它出自1852年的一次海上航行。

　　Known as hardtack, such biscuits were prized for their long shelf lives, making them a vital source of sustenance for sailors far from shore.

　　这种以硬面包闻名的干粮，是因为它们长久的保存期限而备受重视的，这使得它们成为了远洋航行的船员的一个关键的给养来源。

　　They were also appreciated by a great economist, Irving Fisher, as a useful economic metaphor.

　　同时，它们还被一位伟大的经济学家---欧文费雪推崇为一个有用的经济学比喻。

　　Imagine, Fisher wrote in "The Theory of Interest" in 1930, a group of sailors ship wrecked on a barren island with only their stores of hardtack to sustain them.

　　假设，费雪在1930年的《利息理论》中写道，一群船员在一次船只失事中落难到了一座贫瘠的岛屿上，只有储备的硬面包来维持生计。

　　On what terms would sailors borrow and lend biscuits among themselves?

　　船员相互间会以何种条件借入和出借干粮呢?

　　In this forlorn economy, what rate of interest would prevail?

　　在这个孤立无助的经济体中，何种利率会占上风呢?

　　One might think the answer depends on the character of the unfortunate sailors.

　　人们或许会认为，答案取决于不幸的船员的人品。

　　Interest, in many people’s minds, is a reward for deferring gratification. That is one reason why low interest rates are widely perceived as unjust.

　　在许多人的头脑中，利息是对推迟满足感的一-种奖赏。这是为什么低利率被广泛地认为是不公平的一个原因。

　　If an abstemious sailor were prepared to lend a biscuit to his crewmate rather than eating it immediately himself, he would deserve more than one biscuit in repayment.

　　如果某位省吃俭用的船员准备把一份干粮借给他的同伴，而不是立即自己吃掉，他会理应得到多于一份干粮的偿还。

　　The rate of interest should be positive- and the sharper the hunger of the sailors, the more positive it would be.

　　利率应当是正的——而且船员的饥饿感越强烈，它会正的越多。

　　In tact, Fisher pointed out, the interest rate on his imagined island could only be zero.

　　实际上，费雪指出，在这个他所设想的岛屿上，利率可能仅为0。

　　If it were positive, any sailor who borrowed an extra biscuit to eat would have to use more than one biscuit in the future to repay the loan.

　　如果它是正的，任何一位借了额外的干粮吃的船员，今后都不得不用多于一份的干粮来偿还这笔贷款。

　　But no sailor would accept those terms because he could instead eat one more piece from his own supply, thereby reducing his future consumption by one, and only one, piece.

　　但是, 没有船员会接受这种条件。这是因为，他可以代之以吃掉自己供给中的多于一份的干粮，因而减少了他未来的消费中的一份，并且仅仅是一份而已。