"reduce in number" is a correct and usable phrase in written English.
You can use it any time you need to describe a decrease in amount. Example: The population of birds in the park has been reduced in number due to the recent cold spell.
But those which have built their business around psychoactive substances will reduce in number or cease to be".
As time passes, the number of infected cases here becomes higher, while the susceptibles reduce in number at this location.
Resource terms can reduce in number if two collocated resources with identical rates have time intervals that meet.
This infection results in the persistent activation of immune system, and consequently, CD4+ T lymphocytes would greatly reduce in number resulting in body's ability to fight against HIV infection.
The Editors in Chief of both journals are fully aware that this transition will take some time and therefore it is expected that the number of experimental/basic science studies in KSSTA will reduce in number over a period of time and in the future any such studies submitted to KSSTA shall be cascaded to JEO; this being optional to authors, of course.
The scales do not increase in number as the snake matures nor do they reduce in number over time.
"We may reduce in numbers; that would actually be a help, though the chances of it happening within the next century is very small.
Thus, earliest microadenomas were reduced in number due to reduced Cdk4 activity.
Although much reduced in number, Protestantism persisted in France.
The structures were also reduced in number and unevenly distributed throughout the nuclear membrane.
By the end of the war, the Chetniks were greatly reduced in number.
