Usage of "Stand for"

[Genzo]

In my class, I was taught that I can rewrite the sentence:
"Before you go out, you need to finish all your homework."
To the following one:
"Before going out, you need to finish all your homework."

When I read an IELTS writing, there was a sentence:
""Use of the tube has been relatively stable, falling from around 27% of commuters in 1960 to 22% in 1980, but climbing back to reach 25% by 2000"
I don't understand how we can use 'falling' and 'climbing' in a way like that.
Could someone tell me the original form of the above sentence? Or the grammar used in it? Thank you very much.

[Alan]

Hi Genzo,

The grammar of this construction is the use of the participle referring back to the original subject. What this means is that the 'use' is both falling(declining) and 'climbing back' (coming back to what it was). It is a method of reducing the length of the sentence which in its entirety would read: Use of the tube has been relatively stable, although it has been falling from around 27% of commuters in 1960 to 22% in 1980, but has been climbing back to reach 25% by 2000.

Hope this makes sense,

Alan
_________________
English as a Second Language
You can read my ESL story Present Simple

[Genzo]

Sorry. I quoted the wrong sentence. The right one must be:
"They made up 41% in 1998, falling slightly to 37% in 2000"

[Alan]

I don't follow.

Alan
_________________
English as a Foreign Language
You can read my EFL story Progressive Forms

[Genzo]

Is there a mistake in the latter sentence? It is in one of the example essays my teacher gave me, but she said that they was the real essays made by the candidates so it might contained some mistakes.
Besides, the whole passage is as follows:
"The second biggest group of users is aged between 31 and 50. They made up 41% in 1998, falling slightly to 37% in 2000. When combined with the 16-30 age gruop, over 94% of users in 1998 were between 16 and 50."