depreciate by meaning in English

以…(数字)贬值：

the car's value will depreciate by about $ 5000 in the first year
汽车价值价在第一年将折旧约五千美元。
its value against the dollar has depreciated by about 20 % since late october
从去年10月以来，它对美元的比价已经贬值了20。
taking account also of trading on the previous day, the exchange rate had depreciated by a total of about 15 percent
在此情况下，港元因而迅速滑落。连同上日的跌幅计算在内，港元在两日内大约下跌了15%。
starting at the time of purchase, the market value of the car depreciated by 20 percent of its purchase per year
我认为，后半句的理解有问题，汽车的市值每年在其购买价的基础上贬值20%，那么除当年外，以后每年的市值不变？
but actually the realistic values of these strategies are greatly depreciated by the nuclear problem of north korea, for, if korea peninsula comes to the worst condition, the great powers around cannot benefit from that, and nevertheless pay for that
但是，北韩的核问题事实上大大折扣了这些战略的现实的价值，因为，如果韩半岛真的出现最坏的状况，他们非但得不到任何好处反而为此付出代价。