Intransitive use of the verb “reduce”
I know that the verb “reduce”, which is often followed by an object, can also be used intransitively, as dictionaries show very clearly. What I am unsure of, however, is whether “reduce” could actually be used to replace verbs like “decrease”, “fall” and “drop” in sentences such as the ones below:
The number of complaints has decreased sharply in the last quarter.
The company’s profit will probably fall 4.5 % next semester.
Domestic sales dropped 10% last year.
Foreign investment has been decreasing steadily over the last years.
The use of “reduce” in these sentences does somehow sound very strange to me, indeed it sounds wrong, but I wonder if, even if perhaps unusual, it is in any case grammatically correct.
I got a bit confused when I saw these examples in the Oxford Dictionary, to illustrate the meaning “become smaller or less in size, amount or degree”:
The number of priority homeless cases has reduced slightly.
At the same time the number of senior managers has slightly reduced.
The report says that the amount of summertime rain will increase by 20% in the west while slightly reducing in the east.
Instead the amount of the loan reduces with the depreciation of the sum lent, commonly at the rate of 4% per annum for five years.
The cover reduces from year to year as the loan amount repayable drops.
Criminal damage reports also reduced, falling from 30 in June and July to 14 in August and September.
Solution 1:
The construction sounds a bit clunky to me too. However, it is included in most dictionaries and there is evidence of use: searching Google Books for "has reduced slightly" or "has reduced in the" shows a fair number of published examples. Still, Google NGram shows that it is still significantly rarer than the use of other verbs such as 'fall' or 'decrease' (especially taking into account that the search results will include some transitive false positives).
Solution 2:
It seems like the intransitive form of reduce is usually nothing more than an elision of the passive voice of the transitive form:
The number of complaints has (been) reduced sharply in the last quarter.
Domestic sales (were) reduced (by) 10% last year.
In particular, numbers or their equivalents can often be reduced passively. Whether or not the intransitive reduce "sounds right" to one's ear in these cases depends almost entirely on the extent and reasonableness of the elision. If not elided, the construction likely will sound perfectly normal to most native speakers.
In cases where the usage is not an elision of the passive voice, it can sound odder to one's ear:
The cover reduces from year to year as the loan amount repayable drops.
This type of construction could possibly leave people expecting an object for the verb ("What does the cover reduce? My overall liability?") until they figure out from context that reduce is being used intransitively.
So, in direct answer to your question, I think one can easily use reduce in your first and third sentence, while one would likely want to avoid it in your fourth, due to the lack of possible passive voice. In the second sentence, you would likely reword it slightly to introduce the passive voice if you wanted to use reduce:
The company’s profit will probably be reduced by 4.5 % next semester.