占める and particles

Question

My book says that

AはBの[割合]を占めている

is a structure used to say

A accounts for [fraction] of B

So far, so good. But it also provides the following two alternative structures, which bother me:

AのBに占める割合は~

Bに占めるAの割合は~

What I don't really understand is why in the first structure B, that's supposed to be the whole which A is a part of, is marked with the particle を, while に is used in the other two structures.

Moreover, I could not find any example that uses the second structures.

Are these alternative structures commonly used? And how can I wrap my head around which of the whole and the part is marked by what particle?

Answer 1

A は B の [割合{わりあい}] を占{し}めている

A の B に占める割合は~

B に占める A の割合は~

Before saying anything, I will say that B represents the whole and A represents a part of it. 「割合」 means "percentage".

The next thing I am going to say is that all three phrases above are common, grammatical and natural-sounding.

Now, moving onto the nitty-gritty..

「～～を占める」

We use 「を」 when preceded directly by the percentage/fraction.

• 「日本人は日本の人口の９５％ を 占めている。」

• 「日本の人口の９５％ を 日本人が占めている。」

「～～に占める」

We use 「に」 when preceded directly by the object being discussed.

• 「日本の人口 に 占める日本人の割合は９５％である。」

• 「中国人の全{ぜん}外国人{がいこくじん}観光客{かんこうきゃく} に 占める割合は３０％です。」