1·Professor Pretty and his colleagues calculated the externalities of British agriculture for one particular year.
普雷蒂教授和他的同事计算了某一年英国农业的外部性。
2·The fact that burning fuel creates these "negative externalities" does not imply that no tax on fuel could ever be too high.
燃烧燃料产生这些“负外部性”的事实并不意味着燃油税不会太高。
3·Economics is precise about the tax that should, in principle, be levied to deal with negative externalities: the tax on a liter of fuel should be equal to the harm caused by using a liter of fuel.
从经济学的角度来看，为了应对负外部性，原则上应该征收的税收是准确的：对一升燃料征收的税应该等于使用一升燃料所造成的危害。
4·This also an example of positive externalities.
这也是正外部性的一个例子。
5·Urban planners know this problem all too well. After all, traffic is filled with negative externalities.
当然，城市的交通规划者们对于这个问题也是很清楚的，毕竟，城市交通总是充斥了各式各样的负外部性问题，例如某位司机轻踩刹车的微小行为，就会引发一连串的连锁效应，对众多其他司机产生影响。