Hey Soo Jeong!

That is a brilliant question and I'm so glad you asked!

To answer your question as clearly as possible,

Q: Can you say “a fewer _____” in a sentence?
A: Although it may not be as common, yes you can.

If you would like to check out some example sentences, try Google News or the Ludwig website:
https://ludwig.guru/s/a+fewer

In my opinion, the reason why the expression “a fewer ____” is not used commonly is because the word “fewer” has the meaning of “더 적은” which fundamentally refers to some quantities in almost all of sentences. I personally wouldn’t say “a fewer ____” in a sentence very often, but if your question is “is it wrong to say “a fewer ____?” then my answer is no, it is not wrong.

For instance,

if you want to say
“[지금 현재 자동차 수에 비해,] 더 적은 수의 자동차는 공기 오염을 더 방지 할 수 있다.”

You could say something like,
“[Compared to the number of existing cars,] a fewer cars can prevent air pollution further.”

or

“A fewer number of cars can prevent air pollution further.”

In the case of our sentence "Also, fewer goods and services are produced," I actually think it is perfectly fine to translate it as "더 적은 재화와 용역이 생산된다." because contextually speaking, it is fitting just fine and indeed more realistic.

Frankly, I wouldn't worry about it too much as this just seems like another “a beer” vs “a can of beer” kind of situation to me (which I explained in another video I believe). One could always say “this is not grammatically correct”, when the other person might say “but all of my English speaking friends say this.”

I personally believe it would be better if you try not to think like “putting an 'a' in front of 'fewer' is wrong because fewer is 비교급 and it must be translated this way… this is grammatically wrong…” this will only give you a headache in my humble opinion, haha.

Instead, look it up on Google News, Quora, Reddit, YouTube, Naver, and many other English learning resources online and see it for yourself if something is truly “grammatically wrong” or not. Watch TV series, and movies in English... and see how other people use it!

I hope this answered your question. Also, just for your information, please try to write your question in English next time! I sincerely appreciate your enthusiasm. :)

Best regards,

- Mason (Instructor)