占める and particles


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?




> 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。」




> 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。」

