英语介词的用法the graph shows the increase in the ageing population

英语介词的用法
the graph shows the increase in the ageing population in japan,sweden and the USA.it indicate that the percentage of elderly people in all three countries is expected to increase to almost 25％ of the respective population by the year 2040
这段话里的介词都是怎么用的，有些地方用of 有些地方用for，还有些地方用in，我都弄不清楚为什么这么用，谁能给我讲一下，好的话会加分！！

不要从网上复制一大堆我看不懂的东西好吗？尽量能给我讲清楚为什么这里面要这样用