不幸的是，除非中位数选民的效用值恰好等于平均效用值。选举一般不会产生一个有效率的结果。
Unfortunately, voting does not result in an efficient outcome generally, and only does so when the average value equals the median value.
总效用等于平均效用和橙子数量的乘积——即是说，这是平均效用的定义，该定义符合我们平常所用“平均”一词的含义。
Total utility is equal to the product of the average utility and the number of oranges — i. e. , this is a definition of average utility consistent with our usual use of the term average.
如果把黄页目录的每年使用数量除以相同大小广告所需费用，就可看到平均花费一块钱，哪种黄页目录能提供最大效用。
If you then divide directories' uses-per-year figures by their charge for the same size AD, you'll see which directory provides the highest number of USES per dollar.
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