falling into

"The pie charts compare the proportions of people falling into three distinct age groups in Yemen and Italy in two different years."

原文:http://ielts-simon.com/ielts-help-and-english-pr/2014/01/ielts-writing-task-1-pie-charts-1.html

這段話我看得出來意思是

"這張圖用來比較葉門和義大利在三種年紀區間的人口比例"

但我可能會寫成

"The pie charts compare the proportions of people in three distinct age groups in Yemen and Italy in two different years."

其實我看不太懂得是" falling into"的用法,有沒有其他和這邊類似的用法?