Query on CR - " Recent studies show that people between "

[chetans21]

I have searched for the following Q but could not find any discussions on the same and the source is mentioned as MGMAT .
The Q is --
Recent studies show that people between the ages of 13 and 55 produce 65 pounds more garbage per year now than they did in 1995. This increase has led to a higher percentage of the total garbage produced by all age groups. This age group constitutes a growing percentage of the population, so it partially explains this rise.

Which of the following can be concluded from the passage above?

A) People over the age of 55 produce less garbage than children below the age of 13.
B) The population has risen since 1995.
C) People between the ages of 13 and 55 are more than half of the current population.
D) Before 1995 people below the age of 13 and over the age of 55 produced a higher percentage of garbage than they do now.
E) People between the ages of 13 and 55 produce more garbage than those that are younger or older

Query--
The usage of This increase has led to a higher percentage of the total garbage produced by all the age groups. is slightly confusing..
when we are talking of all the groups, HOW can all the groups simulatenously increase there %s..
say <13 and >55 GROUP was producing 56% and remaining 44% was being produced by the group between 13 and 55.. NOW how can both group increase their %, it will go above 100%.
SO I presume, it means average per person in all groups has increased

Ofcourse, the logic for C as the answer fits in properly then.