The phrase "a decrease in the number" is correct and usable in written English.
It can be used when discussing a reduction in quantity or frequency of something, often in statistical or analytical contexts.
Example: "The report indicated a decrease in the number of participants compared to last year."
Alternatives: "a reduction in the count" or "a decline in the quantity".
A decrease in the number of administration jobs has pushed up average earnings during the period of pay restraint.
"We'll see a decrease in the number of V.C. firms as well as the number of venture capitalists".
Wages increase only with an increase in capital or a decrease in the number of workers.
Local market conditions have also contributed to higher construction costs, including a decrease in the number of contractors submitting bids and an increase in insurance costs.
Farage has claimed that yesterday's figures showing a decrease in the number of Romanians and Bulgarians working in the UK since January are statistically insignificant.
And that has led to what seems to be a decrease in the number of abortions performed after ultrasounds that reveal the sex of a fetus.
At the same time, there was a decrease in the number of Hispanic professionals and an ethnic category described as "other" who were living in such tight spaces.
But the newspaper added that even if the problem can be partly solved through a decrease in the number of conscripts, the upcoming reduction will be the widest.
We will see a decrease in the number of businesses in the 20-employee range because it's becoming impossible to make it because of the cost of operation.
(AP) NEW JERSEY ELIZABETH: JAIL PLAN SHELVED -- Citing a decrease in the number of young detainees, Union County officials have scrapped plans to build a juvenile jail here.
In sectors such as childcare, where the vast majority of employers are small, this is likely to lead to a decrease in the number of employers getting involved.
