A survey by the National Council of Churches showed that in 1986 there were 20,736 female ministers, almost 9 percent of the nation's clergy, twice as much as 1977.
我在Merriam-Webster's Online Dictionary, 11th Edition中查到for的用法“used as a function word to indicate duration of time or extent of space ”但这里接的应该是一个时间段而不是时点啊?